To improve the performance of a diaphragm switching plate to be inserted and removed into and from between lenses.

Photographing lenses of a film unit with lenses having a diaphragm switching mechanism are composed of two elements. A horseshoe-shaped spacer 38 is interposed between these lenses and a recessed surface 38a which is recessed by one step is formed at the spacer 38. The diaphragm switching plate 48 is inserted and removed into and from the recessed part 38a. As a result, the plate 48 does not strike the lenses in insertion and removal and the run out of the plate 48 to the direction of the optical axis can be prevented.