and a condenser lens 17 a filter attenuating member 21 and an energy measuring device 19 are disposed on the transmission side of the beam splitter 16 the condenser lens 17 the filter 21 and the energy measuring device 19 compose a laser energy measuring unit 32 the scanner mirrors 5 a and 5 b are positioned by being rotated centering on axes of rotation respectively by scanners 6 a and 6 b the total reflection mirror 4 c the scanners 6 a and 6 b and the f u03b8 lens 3 are mounted on a machining head 7 the machining head 7 is arranged to be movable in a direction of an arrow z by a z axis motor 13 a printed circuit board 8 is fixed on an x y table 9 movable in directions of arrows x and y while facing the f u03b8 lens 3 the size of a machining area 10 defined by the diameter of the f u03b8 lens 3 is about 50 mm u00d7 50 mm next a machining operation of the laser machining apparatus 31 will be explained prior to machining the f u03b8 lens 3 is positioned in the direction of the arrow z based on a surface of the printed circuit board 8 and a center of the machining area 10 to be machined is positioned on an optical axis of the f u03b8 lens 3 the two step cylinder 11 is also operated to position the optimum mask hole 12 a for the diameter.