To provide a laser beam machining apparatus capable of improving the laser beam machining quality by performing the laser beam machining constantly at a focal position even when the height of a machining surface of a work is varied.

The laser beam machining apparatus comprises a laser beam emission means 12 to emit laser beams L, a laser beam deflecting means 14 to deflect the laser beams L in an arbitrary direction, a laser beam condensing means 16 to condense the laser beams L, a laser beam reflecting means 18 to reflect the laser beams L in an arbitrary direction, and a control means 22 to control the laser beam deflecting means 14 and the laser beam reflecting means 18 so that the sum of the optical path length from the turning point of the laser beams L in the laser beam condensing means 16 to the reflecting point of the laser beams L in the laser beam reflecting means 18, and the optical path length from the reflecting point of the laser beams L in the laser beam reflecting means 18 to the irradiating point at which a work W is irradiated with the laser beams L is nearly equal to the focal distance of the laser beam condensing means 16.