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Harmony, Create, and Challenge
Architecture has a great influence on rows of houses or the climate, and occasionally may also change the environment of a community.
We aim always to be an organization which can design not only architecture, but also the surrounding space, being conscious of “architecture in the environment.”
We have the spirit of taking responsibility for the improvement of culture through architecture, and keep challenging with reliable technology based on many experiences.


Message From the President

To evolve into a company that will last 100 years for the next 50 years
– Aspirations and beliefs for heights, and its pride as an expert in shaping buildings and towns –

ACA SEKKEI celebrated its 50th anniversary in July 2020. Since its founding in 1970, it has always inherited the stance of taking on challenges. With awareness and pride as a group of architectural design specialists, we have contributed widely to society through our design activities, aiming for attractive architecture that is trusted and pleased by our clients.
We will respond to the changing sophistication and complexity of society, pursue new technologies with aiming for highly worth design work. We will pursue “architecture in the environment” that is harmonized with the natural environment and local communities and create architecture that contributes to the creation of a sustainable society.
As construction demand is declining due to today’s declining birthrate and aging society, we will focus on already opened bases in Southeast Asia, where development is expected in domestic local cities and future development, and always challenge undeveloped areas with foresight. We will continue to develop and grow into a company that can meet all social needs and create new value to further refine and evolve our efforts so far and make a further leap forward in the next 50 years.
Yoshinori Kobayashi, President

Company Profile

First-Class Registered Architect Office
Registration Nagano Head office
Registered by Governor of Nagano Prefecture (Register No. M77312)
Management Architect : Hidekuni Tatsuno
Tokyo Branch
Registered by Governor of Tokyo Metropolitan (Register No. 53789)
Management Architect : Kouji Sato
Establishment July 15 , 1970
Capital 40,000,000 yen
Employees 100(male 77, female 23)
(Total members of ACA Group 142)
Registered Japan 1st-Class Architects/Engineers : 45
Building services architects : 3
Quantity surveyors : 9
In charge of structure : 8
In charge of mechanical and electrical design : 13
Scope of
1. All services related to architecture(including planning, design, structural engineering, mechanical and electrical design, air conditioning, sanitation, interior design, quantity survey, supervision etc.)

2. Urban design, urban redevelopment planning on various applications concerning development and more (including Urban redevelopment project, Survey / planning / design related to town development)

3. Management and consulting (including inspection, investigation, estimation, existing building survey・seismic system diagnosis, renewal、PFI、FM、medical consulting service, etc.)

4. Environmental design and civil engineering (including Environmental design, Environmentally friendly and energy saving proposal, Landscape design)

5. Information processing and survey using a computer(including CG、BIM、Environment Simulation )

6. Surveys (Surveys for projects related to architecture and civil engineering, etc.)

7. Overseas project (including various scope of work mentioned above)

ACA SEKKEI Organization Chart

Branch/Overseas Office

Nagano head
2360-4 Yanagihara, Nagano City, Nagano 381-0012, Japan
TEL. +81-26-296-8300 FAX.026-296-8350・・・MAP
Tokyo branch
PMO-Kanda-Manseibashi Bldg.4F, 1-3-9 Kandasudacho, Chiyoda-ku,Tokyo 101-0041, Japan
TEL. +81-3-5297-8177 FAX.03-5297-8176・・・MAP
branch office
2-8-10 Soyano, Matsumoto City, Nagano 390-0842, Japan
TEL. +81-263-88-2224 FAX.0263-88-2237・・・MAP
Joetsu branch
4-3-19 Nakamachi, Joetsu City, Niigata 943-0831, Japan
TEL. +81-25-530-7130 FAX.025-530-7137・・・MAP
Ho Chi Minh
12F – Havana Tower, 132 Ham Nghi Street, Ben Thanh Ward, District1,Ho Chi Minh City, Viet Nam
TEL. +84-8-3821-2332 ・・・MAP
Yangon Office No.0204, Sakura Tower, 339 Bogyoke Aung San Road, Kyauktada Township, Yangon, Myanmar
TEL. +95-1-255217 ・・・MAP


1999 change of the company’s name to ACA SEKKEI CO., LTD
2001 ISO9001 certification
2005 Participation in PFI projects
2006 Establishment of ACA TOSHIKIKAKU CO., LTD
2007 Establishment of the Tokyo branch office
2008 SANYU Facilities Design CO., LTD participates in ACA GROUP
2011 Transfer of management rights to ACA TOSHIKIKAKU CO., LTD
2012 Establishment of the
Ho Chi Minh Office

Establishment of ACA KENBI CO., LTD
2013 Establishment of the Yangon Office
Establishment of the ACA CONSULTING CO., LTD
2014 Establishment of the Matsumoto branch office and the Joetsu branch office
Agreement conclusion with DESIGN 2000 CO., LTD
Establishment of the ACA Architectural Inspection CO., LTD
2018 Merging SANYU Facilities Design CO., LTD and ACA SEKKEI MATSUMOTO CO., LTD
2020 50th anniversary


Executive officers President and Chief Operating Officer
Yoshinori Kobayashi, Registered Japan 1st- Class Architect

Vice President
Keiji Yumoto, Registered Japan 1st- Class Architect

Managing Executive Officer
Yoshio Sakamoto, Registered Japan 1st- Class Architect

Managing Executive Officer
Keiichi Sekizaki

Executive Officer and General Manager of Tokyo Branch
Kouji Sato, Registered Japan 1st- Class Architect

Managing Executive Officer
Tsutomu Kaise, Registered Japan 1st- Class Architect

Managing Executive Officer
Kakihisa Baba, Registered Japan 1st- Class Architect

Managing Executive Officer
Jinichi Kasuga, Registered Japan 1st- Class Architect

Managing Executive Officer
Susumu Tokutake

Member of
the Board
Representative Director
Taiichi Tatsuno, Registered Japan 1st- Class ArchitectDirector

Namio Sekiguchi, Registered Japan 1st- Class Architect

Yoshinori Kobayashi, Registered Japan 1st- Class Architect

Keiji Yumoto, Registered Japan 1st- Class Architect

Senior Adviser Hidekuni Tatsuno, Registered Japan 1st- Class Architect