The stereoscopic imaging optical system 1 includes, in order from an object side thereof to an image plane side thereof, a front group Gf including a first front group Gf1 with a center axis C1 thereof as center and a second front group Gf2 with a center axis C2 thereof arranged parallel with the center axis of the first front group as center, a front deflection group Gfd located on an image plane side of at least one of the first front group Gf1 and the second front group, and a rear group Gb that is located on the image plane side of the front group Gf and the front deflection group Gfd and has a single center axis.
