PURPOSE: To inspect the presence of the leak of painting machinery without disassembling the painting machinery.

CONSTITUTION: Air regulated in pressure is sent in an air introducing port 33 and a paint introducing port 35 of a painting machinery, for example, a painting gun 30 from a regulator L1 and the operation state of a valve is inspected by detecting the amt. of the air flowing out of a nozzle 34b by a flowmeter FG and the outflow amt. from the nozzle 34b is measured by a leak gauge LG in such a state that the supply of air to the air introducing port 33 is cut off to inspect the leak quantity of the painting gun.