An optical path bending optical system includes, in order from the object side, a first lens unit, a second lens unit with negative power, and at least one lens unit with positive power. When the magnification of the optical system is changed in the range from a wide-angle position to a telephoto position, the lens unit with positive power is moved along the optical axis. The first lens unit is constructed with a prism including a reflecting surface for bending the optical path, an entrance surface, and an exit surface, and has negative power. The entrance surface of the prism is configured as a curved surface with negative power which is rotationally symmetrical with respect to the optical axis.