PURPOSE: To perform working at the working speed and laser light output meeting the form of working and to improve working efficiency by determining the working speed or the output of laser light according to the shape, thickness and material quality of a work and performing working with the controlled laser light output or at the controlled working speed.

CONSTITUTION: A working speed and the output of laser light which are to serve as a reference for working are first sotred in a numerical control device 1 provided with an arithmetic function. The working speed is then partially determined according to the concrete shape of a work and is stored in the device 1. The determination thereof is transmitted to a control device 2 for a driving part which controls a table 2 and a focusing head 4 according to the determination. The output of the laser light is at the same time calculated in accordance with the determined working speed by the device 1 and is outputted to a control device 5 for laser output to control a laser oscillator 6. The actual working speed is then fed back to the device 1 and if there is a difference between the determined speed and the actual speed, the output of the laser light is changed. An equally good result is obtd. as well by determining the output of the laser light and controlling the working speed in accordance with the output of the laser light to perform working.