An image forming apparatus includes a main assembly including an opening, a cartridge tray for dismountably supporting a cartridge, an openable member for opening and closing the opening, with the cartridge tray being provided at one end portion side, and a limiting member. An urging member urges the cartridge tray from an inner position in the main assembly to an outer position, and a locking member moves between a regulating position and a non-regulating position in interrelation with movement of the openable member. When the openable member is closed, the locking member moves to the regulating position at which the locking member engages with the cartridge tray to push it to the inner position and limits movement of the cartridge tray toward the outer position, and when the openable member is opened, the locking member moves to the non-regulating position at which the locking member disengages from the cartridge tray.