To provide a laser beam machining apparatus and a laser beam machining method in which high cutting capacity is obtained without using any special optical element for the deformation of the beam profile.

The laser beam machining apparatus comprises a YAG laser (a laser beam source) 5 to emit fundamental harmonic laser beams λ1, a second wavelength conversion element 7 of non-linear optical crystals which converts the fundamental harmonic laser beams λ1 into the fourth harmonic radiation (harmonic) laser beams λ4 with the beam sectional shape being flattened in one direction by the walk-off phenomenon, and outputs the laser beams, an optical system 3 to condense the fourth harmonic radiation laser beams λ4 and irradiate a workpiece 2 with the laser beams, and a moving mechanism 4 to move the position of irradiation on the workpiece 2 by relatively moving the fourth harmonic radiation laser beams λ4. The moving mechanism 4 matches the moving direction of the fourth harmonic radiation laser beams λ4 with the flattening direction.