To provide an image forming apparatus capable of preventing a main unit of the apparatus from moving and falling from a desk when a light-shielding bag is pulled out even if a film package is loaded without cutting one end of the light-shielding bag.

The image forming apparatus 40 has: a film loading means capable of loading a film package holding a plurality of sheet films in a light-shielding bag in a light-tight state and capable of moving between a loading position of the film package pulled out of the main unit of the apparatus and a carrying position in the main unit of the apparatus; and locking means 71a, 45a to lock the film loading means located in the main unit of the apparatus. The image forming apparatus 40 is configured such that after loading the film package, the film loading means is moved to the carrying position in the main unit of the apparatus and locked by the locking means, and then the light-shielding bag can be removed from the main unit of the apparatus. A sheet film is carried and exposed to form an image. The image forming apparatus 40 is configured as a desktop one and the locking means unlock the film loading means when the force produced during removal of the light-shielding bag exceeds a predetermined value.