To improve the substantial service life of a boosting valve without enlarging a pneumatic circuit.

The piping on the output side of a regulator 3 is branched in two ways, and one branched piping is connected to an input port 1a of a solenoid switching valve 1, and the other is connected to a boosting valve 2a. The output from the boosting valve 2a is connected to an input port 1b of the solenoid switching valve 1 through a tank 2b. An output port 1c of a solenoid switching valve l is connected to a test head 5 and a test head stand 6 through a regulator 4. The solenoid switching valve 1 supplies the compressed air through the boosting valve 2a when the air cylinder of the test head 5 and the test head stand 6 is driven, but when the cylinder is stopped, the solenoid switching valve can be switched so as to supply the compressed air without through the boosting valve 2a.