An image forming device comprising: a main casing defining an accommodation space; a holder unit configured to be movable in a moving direction between an accommodated position in which the holder unit is accommodated in the accommodation space and a pull-out position in which at least part of the holder unit is outside the accommodation space; a plurality of image bearing members that are held by the holder unit and that are juxtaposedly arrayed in the moving direction with intervals between neighboring image bearing members; a plurality of developing units that are held by the holder unit in one to one correspondence with the plurality of image bearing members; a plurality of toner boxes that are detachably attachable to the holder unit in one to one correspondence with the plurality of developing units, each toner box being detachably attached to the holder unit at the pull-out position, each toner box including: a toner container accommodating therein toner and formed with an opening through which toner in the toner container is to be supplied to the corresponding developing unit; and a shutter movable between an open position for opening the opening and a closed position for closing the opening, characterized by a plurality of first acting portions (33, 123), wherein, for each of the plurality of toner boxes, a first acting portion (33, 123) is provided at the holder unit and is configured to be movable between a first position providing the open position of the respective shutter and a second position providing the closed position of the respective shutter; by a plurality of second acting portions (34, 124), wherein, for each of the plurality of toner boxes, a second acting portion (34, 124) is provided at the holder unit and is configured to be movable between a third position providing the open position of the respective shutter and a fourth position providing the closed position of the respective shutter; and by an abutment member provided in the main casing and configured such that the first acting portion (33, 123) abuts against the abutment member when the holder unit is on its way to the accommodated position from the pull-out position while the first acting portion (33, 123) is at the second position, to thereby move the first acting portion (33, 123) to the first position, wherein the abutment member is configured such that the second acting portion (34, 124) abuts against the abutment member when the holder unit is on its way to the pull-out position from the accommodated position while the second acting portion (34, 124) is at the third position, to thereby move the second acting portion (34, 124) to the fourth position. a main casing defining an accommodation space; a holder unit configured to be movable in a moving direction between an accommodated position in which the holder unit is accommodated in the accommodation space and a pull-out position in which at least part of the holder unit is outside the accommodation space; a plurality of image bearing members that are held by the holder unit and that are juxtaposedly arrayed in the moving direction with intervals between neighboring image bearing members; a plurality of developing units that are held by the holder unit in one to one correspondence with the plurality of image bearing members; a plurality of toner boxes that are detachably attachable to the holder unit in one to one correspondence with the plurality of developing units, each toner box being detachably attached to the holder unit at the pull-out position, each toner box including: a toner container accommodating therein toner and formed with an opening through which toner in the toner container is to be supplied to the corresponding developing unit; and a shutter movable between an open position for opening the opening and a closed position for closing the opening, characterized by a plurality of first acting portions (33, 123), wherein, for each of the plurality of toner boxes, a first acting portion (33, 123) is provided at the holder unit and is configured to be movable between a first position providing the open position of the respective shutter and a second position providing the closed position of the respective shutter; by a plurality of second acting portions (34, 124), wherein, for each of the plurality of toner boxes, a second acting portion (34, 124) is provided at the holder unit and is configured to be movable between a third position providing the open position of the respective shutter and a fourth position providing the closed position of the respective shutter; and by an abutment member provided in the main casing and configured such that the first acting portion (33, 123) abuts against the abutment member when the holder unit is on its way to the accommodated position from the pull-out position while the first acting portion (33, 123) is at the second position, to thereby move the first acting portion (33, 123) to the first position, wherein the abutment member is configured such that the second acting portion (34, 124) abuts against the abutment member when the holder unit is on its way to the pull-out position from the accommodated position while the second acting portion (34, 124) is at the third position, to thereby move the second acting portion (34, 124) to the fourth position.