1965	Founded Sanwa Denki Gijutsu Kyoryoku Co., Ltd. (spun off from Sanwa Denki Kogyo Co., Ltd.) with capital of JPY 2 million.
1967	Opened Kawasaki Mukaigahara Office.
1969	Completed Miyamae Factory and commenced operations. Increased capital to JPY 6 million. Registered as a telecommunications construction business.
1970	Increased capital to JPY 15 million.
1971	Increased capital to JPY 30 million.
1973	Increased capital to JPY 60 million.
1980	Commenced operations at Oyama Factory (Oyama-cho, Shizuoka).

1981	Established Sankyo Denshi Co., Ltd.
1982	Increased capital to JPY 90 million.
1986	Changed company name to SANGIKYO CORPORATION. Increased capital to JPY 180 million.
1987	Completed Yokohama Headquarters and commenced business. Established Fukushima Sangikyo. Saitama Sangikyo Co., Ltd. became an affiliate of the Sangikyo Group.
1988	Completed Fukushima Factory and commenced operations.
1990	Increased capital to JPY 200 million.

1991	Completed Saitama Factory and commenced operations. Opened Kansai Branch and commenced business. Completed Fuji Factory and commenced operations.
1993	Registered as an electrical construction business.
1996	Established Sangikyo Media Systems Co., Ltd.
1997	Obtained ISO 9001 certification for the Production Division.
1998	Obtained ISO 9001 certification for the System Division. Increased capital to JPY 263 million.
1999	Registered as a General Type II Telecommunications Carrier. Obtained ISO 14001: 1996 certification.
2000	Increased capital to JPY 296.6 million.

2001	Commenced operation of Sangikyo Group knowledge platform "Cyber Manual." Obtained ISO 9001: 2000 certification.
2002	Established Sangikyo Facility Management Co., Ltd. Released ETC field strength measuring instrument (commonly known as "ETC-Moni").
2004	Released screen-transfer remote desktop system "Platform V System."
2005	Obtained ISO 14001: 2004 certification.
2007	Obtained PrivacyMark certification (surrendered in 2009).
2008	Established new corporate philosophy: "We will continue to create value through Optimization Thinking."
2009	Obtained ISO 27001: 2005 certification. Merger of Sangikyo Media Systems Co., Ltd. and Sankyo Denshi Co., Ltd. Renamed to Sangikyo EOS Co., Ltd.

2013	Obtained ISO 27001: 2013 certification.
2015	Completed the "MIRAIMA" new headquarters building. Michiyasu Sengoku inaugurated as Chairman and Representative Director. Taichi Sengoku inaugurated as President and Representative Director.
2017	Obtained ISO 9001: 2015 certification. Obtained ISO 14001: 2015 certification.
2018	Launched LED Backhaul®.
2021	Watech Co., Ltd. became a subsidiary.
2023	Completed the "KURAIMA" headquarters building.
2024	Obtained ISO 27001: 2023 certification.
2025	60th anniversary of founding.