To improve machining position accuracy in the laser beam machining for forming fine machining traces in the set arrangement.

A controller outputs the output command of the pulse train signal to a pulse signal supply device at time t3 at which the machining start position D is detected. Thus, the pulse signal supply device outputs the pulse train signal to a laser beam drive circuit, and the laser beam drive circuit outputs the drive signal corresponding to the pulse train signal to a laser beam source. Then, a delay signal generation circuit detects the delay (the timing deviation Dev) from the time t3 at which the machining start position D is detected to time t4 at which the laser beam of the machining intensity is actually irradiated. The controller sets the time width Lt of the low level signal at the second period in the pulse train signal by the timing deviation Dev.