To urgently stop a processing machine by putting on the body of an operator a detected object whose color is the same as a previously set reference color to be detected so that a processed material in a dangerous range and the detected object put on the body are discriminated by colors without having mechanical contact and the detected object only can be detected.

The output side of a color discrimination judging device 9 is electrically connected to the operation control disk 4 of a processing machine 1 through a cable 10. When the color of a detected object 6 is detected by the color discrimination judging device 9, a signal is outputted to the operation control disk 4 through the cable 10 in a moment, and a motor 2 is switched off by the operation control disk 4, and also an emergency stopping device 3 such as a brake device is operated so as to stop the operation of the processing machine 1. Hereby, a body entered in a dangerous range can be safely protected from the processing machine 1. The inside of the dangerous range of the processing machine 1 can be thoroughly monitored flatly or stereoscopically, therefore safety can be improved.