A stereoscopic imaging optical system assembly including a first optical system at least including, in order from an object side to an image plane side, a negative lens and an aperture, the first optical system being rotationally symmetric with respect to a first center axis, a second optical system that is rotationally symmetric with respect to a second center axis parallel with the first center axis, and that has the same construction as, and is located in parallel with, the first optical system, and a variable optical system located in such a way as to intersect the respective optical paths through the first optical system and the second optical system. The variable optical system effects a change of at least either one of focus and vergence.