PURPOSE: To simplify construction and reduce the number of parts, by providing a constitution in which the optical axises of both additional lens are positioned so as to cross to the optical axis of a main lens at the magnification time when two additional lens do not enter the optical path of the main lens together.

CONSTITUTION: When a carriage 31 is brought into contact with a stopper 53 and a main lens 30 is stopped at the unmagnification position, the optical axises of additional lens 40a, 40b are positioned so as to meet at right angles with the optical axis of the main lens 30. In order to change over from this state to a reduction (2), the carriage 31 is moved upward by a driving means 70 by making a solenoid 55 off. Then, the lens 40a, 40b are rotated in a reversed clockwise direction while making each of bearings 41a and 41b as a support, and the lens 40b is placed in layers in front of the main lens 30 so that each optical axis is made to coincide with the other. In case of changing over from the unmagnification to the reduction (1), the lens 40a is placed in layers in front of the main lens 30 so that each optical axis is made to coincide with the other and is stopped.