Clamp system which can confirm that the first clamp device and the second clamp device are safely maintained in the disconnected state from the pressure fluid source

The invention provides a simple clamp system capable of safely maintaining a state in which a clamp device under operation is disconnected from a pressure fluid source. The clamp system according to the invention is to dispose a first connection device (16) and a first valve device (13) and a first pressure switch (19) in a first supply and discharge passage (12) of supplying and discharging pressure fluid from a pressure fluid source (11) to a first clamp device (7). A second connection device (17) and a second valve device (15) and a second pressure switch (20) are disposed in a second supply and discharge passage (14) of supplying and discharging pressure fluid from the pressure fluid source (11) to a second clamp device (9). When the pressure of the pressure fluid of the first supply and discharge passage (12) is higher than a predetermined pressure and the pressure of the pressure fluid of the second supply and discharge passage (14) is higher than a predetermined pressure, a loop (21) is conducted.