An interchangeable lens unit includes a second lens group unit, a focus lens unit, a fourth lens group unit, a zoom ring unit, a focus motor, and a photosensor. The zoom ring unit is arranged to mechanically transmit operational force inputted to a zoom ring to the second lens group unit and the fourth lens group unit. The focus motor is configured to electrically drive the focus lens unit in the Z axis direction with respect to the second lens group unit. The photosensor is configured to detect whether or not the focus lens unit is disposed at a starting point position with respect to the second lens group unit. The starting point position is disposed within the total movement range E of the focus lens unit.