To achieve good imaging performance even when a half mirror is used as a light splitting means.

At least one lens element of an imaging lens is arranged on the rear side of the half mirror 10. At least one of lens elements on the rear side or all constituent elements including an imaging device for photographing 33 on the rear side of the half mirror 10 are arranged in a decentering state with respect to the optical axis Z1 of lens elements on the front side of the half mirror 10. Even when offset of the optical axis is caused by arrangement of the half mirror 10, such offset can be corrected on a camera-main-body side. Thereby, the good photographing performance can be achieved even when the half mirror 10 is used as the light splitting means.