To prevent the reuse of a film unit with a lens.

A groove 36 is formed on the inner peripheral face except a key groove 34a of an engaging hole 34 provided in the end part of a spool 31 and a projected line 40 engaged with the groove 36 is formed on the outer peripheral face except a key 38a of the engaging shaft 38 of a winding knob 10. A film cartridge to be sold generally has no groove in the engaging hole, so that the film unit with the lens can not be reused.