An image forming apparatus comprising: an apparatus body having a replenishing device configured to replenish toner; and a developing device which is demountably mounted to the apparatus body and configured to receive replenishment of toner from the replenishing device, the developing device including an inlet port for receiving the toner replenished from the replenishing device, a first shutter configured to slide to open and close the inlet port, and a first urging member for urging the first shutter in the direction to close the inlet port, the replenishing device including a discharge port for discharging the toner to be replenished to the developing device, a second shutter configured to slide to open and close the discharge port, and a second urging member for urging the second shutter in the direction to close the discharge port, characterized in that the apparatus further comprises an interlocking mechanism (223, 323) configured to cause the second shutter to slide in conjunction with the first shutter configured to slide in the mounting direction in association with the mounting operation for mounting the developing device to the apparatus body, and configured to cause the first shutter to slide in conjunction with the second shutter which is configured to slide in the separating direction, which is the opposite direction from the mounting direction, in association with the separating operation to separate the developing device from the apparatus body, is provided, the direction that the second shutter is configured to open the discharge port is the same direction as the mounting direction, and wherein an urging force configured to be applied by the first urging member to the first shutter when configured to close the inlet port is set to be smaller than an urging force configured to be applied by the second urging member to the second shutter when configured to close the discharge port. an apparatus body having a replenishing device configured to replenish toner; and a developing device which is demountably mounted to the apparatus body and configured to receive replenishment of toner from the replenishing device, the developing device including an inlet port for receiving the toner replenished from the replenishing device, a first shutter configured to slide to open and close the inlet port, and a first urging member for urging the first shutter in the direction to close the inlet port, the replenishing device including a discharge port for discharging the toner to be replenished to the developing device, a second shutter configured to slide to open and close the discharge port, and a second urging member for urging the second shutter in the direction to close the discharge port, characterized in that the apparatus further comprises an interlocking mechanism (223, 323) configured to cause the second shutter to slide in conjunction with the first shutter configured to slide in the mounting direction in association with the mounting operation for mounting the developing device to the apparatus body, and configured to cause the first shutter to slide in conjunction with the second shutter which is configured to slide in the separating direction, which is the opposite direction from the mounting direction, in association with the separating operation to separate the developing device from the apparatus body, is provided, the direction that the second shutter is configured to open the discharge port is the same direction as the mounting direction, and wherein an urging force configured to be applied by the first urging member to the first shutter when configured to close the inlet port is set to be smaller than an urging force configured to be applied by the second urging member to the second shutter when configured to close the discharge port.