An ejector functioning as a vacuum generating mechanism is disposed in a main body constituting a vacuum generating unit, and an atmospheric air introducing valve is disposed between the ejector and a vacuum port. The atmospheric air introducing valve is brought into a valve closed state at times when a negative pressure is generated by the ejector under a condition in which a workpiece is held by the negative pressure generated by the ejector, whereby communication between the vacuum port and the atmosphere is blocked. On the other hand, at times when the vacuum is broken, in which the negative pressure state of the vacuum port is released, the atmospheric air introducing valve is brought into a valve open state, whereby the vacuum port communicates with the atmosphere.