Former Labor Minister Yoshio Yoshikawa notified the ruling Liberal Democratic Party through a secretary on Monday that he will retire from politics at the end of his current six-year term, aides said.
He will not run in July's House of Councilors elections, they added.
The aides said that Yoshikawa's secretaries and others will hold a news conference in the city of Niigata today to announce Yoshikawa's formal retirement.
Yoshikawa, 69, collapsed March 19, and his doctors said he needs an extended hospital stay due to a suspected case of angina.
A former Niigata prefectural assemblyman, Yoshikawa was first elected to the Upper House in 1983. He is currently serving his third term.
Yoshikawa briefly served as labor minister last year under the Cabinet of Prime Minister Yoshiro Mori.