To provide a laser beam machining apparatus and a laser beam machining method capable of realizing the consistent machining and suppressing occurrence of defects.

Laser beams 10 emitted from a laser beam oscillator 1 are transmitted to an emission optical unit 6 via optical fibers 2. After the incident laser beams 10 are condensed by a condensing lens 3 in the emission optical unit 6, the laser beams are reflected by a mirror 5, and further condensed by a condensing lens 4, and a work 9 is machined by irradiating laser beams on a machining part of the work 9. The reflected laser beams 11 reflected from the surface of the work 9 are condensed by the condensing lens 4, transmitted through the mirror 5 and detected by a sensor 7. In a laser beam output control unit 8, the quantity of the reflected laser beams during the pre-registered normal machining is compared with the quantity of the reflected laser beams 11 detected by the sensor 7 to adjust the output of the laser beams 10 emitted from the laser beam oscillator 1.