He graduated from the School of Law and Politics, Kwansei Gakuin University in 1979 and worked for All Nippon Airways.

Suematsu entered politics in 1983, successfully contesting the Hyogo Prefectural Assembly election as a Liberal Democratic Party (LDP) candidate.

In April 2003 Suematsu was elected to his sixth term, winning the highest number of votes in the three-member Tarumi district with 39.4%.

[2] In the election for two Councillors in the Hyogo at-large district, Suematsu finished second behind Shunichi Mizuoka of the Democratic Party of Japan with 33.5% of the vote.

His dismissal was part of a wider purge by the Kishida administration following the assassination of Shinzo Abe and increasing media scrutiny of LDP officials' close ties with the church.