PROBLEM TO BE SOLVED: To enable easy and highly accurate machining for the surface to be worked even if the optical device has a large wave aberration. SOLUTION: This apparatus is equipped with a laser generator 3, which machines the surface 2 of a workpiece 1 by irradiating it with an ultraviolet laser L of a short wave length, and a shack hartmann wave front instrument 4 which has a lens array with a large number of micro lenses arranged to make the reference beam of a desired characteristic enter the lens array, and which thereby measures the wave front from a difference between the image- forming position of a reference beam emitted from each micro lens by making the reference beam of a desired characteristic enter the lens array and the image-forming position of a measured beam emitted from each micro lens by making the measured beam enter the lens array through the surface 2 to be worked. Then, the irradiation of the ultraviolet laser L is optimally controlled, on the basis of the deviation of the image-forming position of the measured beam, using as a reference the image-forming position of the reference beam obtained from the shack hartmann wave front instrument 4; and, simultaneously, controlled positionally by a controller 6 is the driving mechanism 5 that relatively moves the ultraviolet laser L and the workpiece 1.