An intermediate reserve tank for temporarily storing a conductive coating medium is provided in a coating medium supply passage for supplying the conductive coating medium from a color switch valve mechanism to a spray gun. A block valve mechanism for electrically insulating the color switch valve mechanism and the intermediate reserve tank is provided. A coating medium extrusion portion for supplying water or a cleaning solution is connected to a transmission passage between the intermediate reserve tank and the spray gun via a switch valve. When an amount of the coating medium necessary until an end of a coating operation becomes a predetermined amount, the conductive coating medium is extruded by the water or the cleaning solution by switching the switch valve.
