In a lens barrel for holding an imaging optical system that forms an optical image of an object, the imaging optical system comprises an object side lens unit 4 onto which light ray from the object is incident and a reflective optical element 5 having a reflecting surface 5a for bending the light ray exiting from the object side lens unit 4, and in an imaging state, the object side lens unit 4 is held in a manner movable in a direction of the light ray from the object, and while in an accommodated state, the reflective optical element 5 is escaped to an escape position different from a position located in the imaging state.