was a Japanese politician of the Democratic Party of Japan (DPJ), who served as a member of the House of Representatives and the House of Councillors in the Diet.
Nishioka was a native of Nagasaki and graduated from Waseda University.
Nishioka was elected to the House of Representatives for the first time in 1963. He lost his seat in 1983 but was re-elected in 1986. He lost the seat again in 2000 and was elected to the House of Councillors for the first time in 2001.
In 2010, he was elected as the President of the House of Councillors, as a member of the DPJ.