When an air pressure in a tank part drops from a maximum set pressure value to or below at least one restart set pressure value defined to lie in a range between the maximum set pressure value and a minimum set pressure value, a control circuit part operates an electric motor at a predetermined revolving speed. This method permits the production of a lithographic printing plate without causing any deterioration of the developing properties of the PS plate even when the imagewise exposed PS plate is developed within a short period of time after the completion of the laser-exposure. Of the plurality of sensors, at least one of the sensors is located in a position upstream of the excitation source location, and additionally a second of the plurality of sensors is located in a position downstream of the excitation source. The signal driver drives a pulse on the signal wire.