In the 18th House of Councillors regular election in 1998, he ran from a proportional representation district with the National Land Development Corporation as his support group and was elected. He served as Parliamentary Vice-Minister for the Director-General of the Defense Agency in the first Koizumi Cabinet and the first reshuffled Cabinet. Regarding the unpaid pension issue of politicians, he was unpaid for 1 year and 7 months.
Sato did not run in the 22nd House of Councillors regular election in 2010 and retired.