To surely prevent an exposed frame from being exposed again even when the normal inserting and ejecting operation of a film cartridge is not performed and a lock means does not perform essential movement associated with the ejection or the insertion thereof.

This camera is provided with a detection means 5 detecting the existence of the film cartridge by changing its state according as the film cartridge is inserted in/ejected from a cartridge chamber, the lock means 4 capable of being displaced to an acting state where the insertion of the exposed film cartridge is inhibited and a non-acting state where locking is not performed, and a control means 9 starting photographing preparation operation by detecting the insertion of the film cartridge after the means 5 detects the ejection of the film cartridge. Then, the means 4 and 5 are arranged so that the means 5 may change its state associated with the displacement of the means 4 from either state to the other state.