To enable efficient operation of an air blower fan motor at a high speed by attaching a non-contact type sensor at a position close to a rotor and a stator in such a manner that it can be adjusted and controlling phase timing of a motor based on rotor information detected by the sensor.

A fan 121 which circulates gas in a laser cavity and is provided with a plurality of fan blades which are extended in parallel with a fan axis is rotated by a motor provided on the outside of a housing 103 which partitions the laser cavity. This motor is a DC brushless motor and consists of a rotor 303 and a stator 307 which are provided on a drive shaft 301 integrally, and a circuit plate 313 on which a hole sensor 311 is mounted is attached in a heat sink part 317 of an end cap 319. A sensor position is adjusted by adjusting a position in the axial direction of the end cap 319 by a bolt 411, and phase timing of the motor is controlled based on output of the sensor.