To prevent a shutter from being inadvertently opened in the case of taking out a process cartridge by disposing a shutter means and a knob part so that the shutter means can not be opened by making the shutter means in a closed state interfere with the knob part in a state where the knob part is not separated.

A drum shutter member 28 is supported to freely open/close by the rotating motion of a shutter arm 27, and the pawl part 27a of the arm 27 is arranged at a position where it comes in contact with a knob member 21b so that the arm 27 may not be rotated in a direction where the member 28 is opened in a state where a sealing member is not pulled, that is, in a state where the member 21b is not separated. Therefore, the member 28 is not opened in a state where the member 21b is not separated, and it is not until the member 21b is separated that the member 28 can be opened. Therefore, the shutter is prevented from being inadvertently opened in the case of taking out the cartridge B just after unsealing a packing material.