A switching valve is disposed between a pressure fluid supply source and
an ejector in a vacuum suction apparatus. A supply port of the switching
valve is connected to the pressure fluid supply source, and an outlet
port of the switching valve is connected to the ejector. In addition,
when suction pads attract a workpiece under suction and a negative
pressure becomes constant, a valve body is displaced by a negative
pressure supplied through a vacuum port to the switching valve, whereupon
communication between the supply port and the outlet port is blocked.