To perform laser beam machining by generating a laser beam automatically, with a protective mask properly fitted on an operator and with the tip end of a laser torch brought into contact with a workpiece.

A laser torch 13 and a power feeding means 25 for a workpiece 24 are serially connected through a start switch 12, which is designed to close concurrently with a facial shield plate 5 fitted on an operator, and a laser generator 19; a circuit is constituted such that an electric current from the power source is flowed to the laser generator 19 to start the generation when the operator, with the start switch closed by attaching the facial shield plate 5, brings the tip end of the tapered nozzle 16 of the laser torch 13 and the power feeding means 25 into contact with the workpiece 24.