An image forming apparatus for forming an image on a recording medium, the image forming apparatus comprising: a cartridge support member movable between an outer position where a plurality of cartridges (4y, 4m, 4c, 4k) are detachably mountable to the cartridge support member, outside of the main body of the image forming apparatus and an inner position where the plurality of cartridges (4y, 4m, 4c, 4k) are supported by the cartridge support member for enabling image formation, inside the body of the image forming apparatus; a first opening of the main body of the image forming apparatus arranged to allow the cartridge support member to pass through the first opening when the cartridge support member is moved between the inner position and the outer position; a second opening of the main body of the image forming apparatus provided vertically above the cartridge support member and arranged so that at least one of the plurality of cartridges (4y, 4m, 4c, 4k) can pass through the second opening to attach or detach any of the plurality of cartridges (4y, 4m, 4c, 4k) from the cartridge support member; and an opening/closing member movably mounted to the main body of the image forming apparatus and operable to take a closed position that covers the first opening and the second opening and an open position in which the first opening and the second opening are open, the opening/closing member comprises a first opening/closing portion disposed in a movement path of the cartridge support member through which the cartridge support member is operable to move in a pull-out direction from the inner position toward the outer position so as to close the first opening when the opening/closing member is at the closed position and a second opening/closing portion arranged so as to close the second opening when the opening/closing member is at the closed position; and characterized in that said second opening/closing portion is rotatably mounted to the first opening/closing portion and rotatable relative to the first opening/closing portion between a protruding position at which said second opening/closing portion protrudes into the movement path and a retracted position at which said second opening/closing portion is retracted outside the movement path, and said second opening/closing portion is arranged so that when the cartridge support member is moved in a pull-out direction from the inner position to the outer position, the second opening/closing portion is caused to move from the protruding position to a retracted position in the pull-out direction so that the cartridge support member is free to move to the outer position. a cartridge support member movable between an outer position where a plurality of cartridges (4y, 4m, 4c, 4k) are detachably mountable to the cartridge support member, outside of the main body of the image forming apparatus and an inner position where the plurality of cartridges (4y, 4m, 4c, 4k) are supported by the cartridge support member for enabling image formation, inside the body of the image forming apparatus; a first opening of the main body of the image forming apparatus arranged to allow the cartridge support member to pass through the first opening when the cartridge support member is moved between the inner position and the outer position; a second opening of the main body of the image forming apparatus provided vertically above the cartridge support member and arranged so that at least one of the plurality of cartridges (4y, 4m, 4c, 4k) can pass through the second opening to attach or detach any of the plurality of cartridges (4y, 4m, 4c, 4k) from the cartridge support member; and an opening/closing member movably mounted to the main body of the image forming apparatus and operable to take a closed position that covers the first opening and the second opening and an open position in which the first opening and the second opening are open, the opening/closing member comprises a first opening/closing portion disposed in a movement path of the cartridge support member through which the cartridge support member is operable to move in a pull-out direction from the inner position toward the outer position so as to close the first opening when the opening/closing member is at the closed position and a second opening/closing portion arranged so as to close the second opening when the opening/closing member is at the closed position; and characterized in that said second opening/closing portion is rotatably mounted to the first opening/closing portion and rotatable relative to the first opening/closing portion between a protruding position at which said second opening/closing portion protrudes into the movement path and a retracted position at which said second opening/closing portion is retracted outside the movement path, and said second opening/closing portion is arranged so that when the cartridge support member is moved in a pull-out direction from the inner position to the outer position, the second opening/closing portion is caused to move from the protruding position to a retracted position in the pull-out direction so that the cartridge support member is free to move to the outer position.