PURPOSE: To reduce the maintenance cost of the nozzle device of a laser beam machine by detecting the electromagnetic capacity between the front end of the nozzle and a work with 1st and 2nd electrodes and providing a nozzle chip which can be fitted to and removed from a nozzle main body to the lower end parts of the 1st and 2nd electrodes.

CONSTITUTION: The 1st electrode 7 provided with a laser passing path is connected with an electromagnetic capacity detector 14 and electrically insulated from a work 15. The peripheral surface of the 1st electrode 7 is covered with the 2nd electrode 8. The 2nd electrode 8 is electrically insulated from the 1st electrode 7 and work 15 end connected with the detector 14. The electromagnetic capacity between the front end of a nozzle 6 and work 15 is detected with the 1st and 2nd electrodes 7 and 8. A nozzle chip 17 which can be fitted to and removed from a nozzle main body is provided to lower end parts of the 1st and 2nd electrodes 7 and 8. Therefore, the maintenance cost of the nozzle device of a laser beam machine can be reduced.