PURPOSE: To automatically remove oil and volatile gas in a vacuum nozzle and a vacuum hose by mounting the holder of the vacuum nozzle to a main body, providing a presser for pressing and oscillating the holder upwards, and providing a detector which detects that the holder is oscillated against the presser and which then provides a signal to operate a vacuum device for a set period of time.

CONSTITUTION: During cleaning a holder 20 is oscillated upwards about a horizontal shaft 22 by means of a tension spring 26 when taken out of a vacuum nozzle 13. Then a starting switch 17 is turned on. After the cleaning is finished and the holder 20 is enclosed in the vacuum nozzle 13 the holder 20 is exerted with a load and oscillated downwards against the pressing force of the tension spring 26. Then a control rod 23 is lowered and made to abut to the detecting portion 28 of a microswitch 27 to actuate the microswitch 27 for detection. Thereby a vacuum device 5 is automatically operated again and idles for a set period of time to substitute fresh air for gas in a vacuum hose 12 and a dust collecting tank 6, etc.