To provide a laser beam machining device capable of eliminating the deterioration of machining accuracy and movement of a machining position due to the misalignment of the lens.

A laser beam emitted from a laser device 1 is turned into a collimated beam 3 by a collimated beam generating optical system 2, and reaches a transducer 21 of a spot shape to which lens action is applied. The transducer 21 changes the direction of the light beam, performs re-allocation of light intensity, and makes a prescribed output intensity distribution on the surface to be machined 6. When the phase distribution of the transducer of a usual spot shape is set to A and the phase distribution of lens action is set to B, the phase distribution C of the transducer 21 of a spot shape to which lens action is applied is realized by 'A+B'. Zero-order light due to a phase error is generated also in the transducer 21 of a spot shape. However, although the zero-order light due to the phase error becomes a noise component on the surface to be machined, it does not become a peak, since a lens is not used, then machining accuracy is not lowered.