To prevent breakdown of a processing object, resulting from collision of an injection nozzle with the processing object due to the trouble of a back-pressure sensor in the processing apparatus, provided with the back pressure sensor constituted to detect the processing object, by having the injection nozzle come close to the processing object.

In the processing apparatus 1 provided with the back pressure sensor 4, the back pressure sensor 4 is provided with a free-movement detecting sensor 43 for detecting the free movement of the injection nozzle 40, which can freely move in the direction opposing to the injecting direction of the air.