An electrophotographic image forming apparatus includes a print unit that prints an image by an electrophotographic process and has a developer cartridge having a photoreceptor drum. A door opens and closes one side of the print unit to install and remove the developer cartridge. A fixing member is selectively shifted between a first position where the developer cartridge is installed and removed and a second position where the developer cartridge is fixed to the print unit by opening and closing the door.