PURPOSE: To improve the processing speed of laser trimming by adding a 90° reversible rotating mechanism to the pedestal for stage and thereby eliminating waste time for putting in and out of a substrate.

CONSTITUTION: It is confirmed by an angle position detector 13 that the stage 4 is at the position of angle 0° and XY table is at an original point. Then, the substrate to be trimmed is placed on the stage 4. Attraction of the substrate is made through a nozzle 7 for a vacuum hose. The XY table is started, and the stage is shifted to a position where laser trimming is possible, and laser trimmings of circuits a, b, c, d are performed by step and repeat action at the position of angle 0°. After completion of the trimming at the position of angle 0°, the stage 4 is turned by 90°, and the position of angle 90° is detected by an angle position detector 13'. Position of the XY table is corrected to bring the circuit e to the position of the circuit d before turning, and laser trimming of the circuit (e) is performed. The stage 4 is returned to the position of angle 0°, and the XY table is returned to the original point again. Finally, the substrate is taken out to complete the process.