A rotation-linear motion conversion apparatus (10) includes: a rack bar (30) in which a rack gear (32) is formed; a housing (40) that surrounds the rack bar (30); a pinion shaft (20) including a pinion gear (22) that engages with the rack gear (32) and that is inserted inside the housing (40); and a support part (50) that is provided on an opposed surface (41s1), which is opposed to the rack gear (32), of the housing (40) and that supports the rack bar (30) movably in a longitudinal direction of the rack bar (30).