Masao Morinaka (?? ??, born April 9, 1974 in Shizuoka, Japan) is a former professional baseball player who played for the Yokohama BayStars.
He currently works as a batting pitcher for the Yomiuri Giants organization.
Morinaka was drafted by the Yokohama BayStars in the second round of the 1996 amateur draft.
He was a valuable left-handed reliever, but was dropped after only 7 seasons in 2003.
He marked a 2.16 ERA in 41 appearances in 1999, and a 2.38 ERA in 53 appearances in 2000.
He hit a home run at the Koshien baseball stadium in his final season.
He won a silver medal playing for the Japanese national team in the 1996 Summer Olympics before entering the Japanese professional leagues.