An image forming apparatus includes: a housing having an opening; a drum cartridge mountable and demountable through the opening; a toner cartridge mountable and demountable to and from the drum cartridge; a first cover; a second cover, wherein, when the first cover is at the opened position and the second cover is at the closed position, the toner cartridge is allowed to be mounted and demounted to and from the drum cartridge through a part of the opening while the drum cartridge is remained to be mounted to the housing, and wherein, when the first cover is at the opened position and the second cover is at the closed position, a part of the second cover contacts with the drum cartridge and prevents the drum cartridge to be mounted and demounted to and from the housing through a part of the opening.