PURPOSE: To prevent the overflow of a waste liquid from a waste liquid tank and a trouble of a photosensitive material by providing a liquid level sensor detecting the liquid level lower than the full-tank liquid level by the preset liquid quantity.

CONSTITUTION: A liquid level sensor 54 is provided at the top of the tank main body 52 of a waste liquid tank 48, and the liquid level of the waste liquid filled through a waste liquid feed port 56. A liquid level difference of the height (l) is provided between the liquid level L detected by the liquid level sensor 54 and the full-tank liquid level H. When the waste liquid reaches the liquid level sensor 54, an alarm is issued, however development processing can be further continued until the waste liquid reaches the full-tank liquid level H. The operation of a developing device is stopped when the waste liquid reaches the full-tank liquid level H. The operation of the developing device is stopped when a preset period elapses after the signal from the liquid level sensor 54 is received by a control device 36. All the photosensitive material, which is used for development in the developing device 10 until the developing device is stopped after the liquid level L is detected by the liquid level sensor 54, is discharged, thus no adverse effect is given to a photosensitive material during the development work, and a trouble that the waste liquid overflows from the waste liquid tank 48 is prevented.