To obtain a laser beam of a fine beam shape by removing a side lobe from a laser beam having the side lobe.

A laser beam L having a side lobe is reflectively deflected by a mirror 23 and made incident upon a shaping means 10 and a part of beam quantity of a laser beam L' passed through the means 10 is detected by a photodiode 21 to check whether the beam L is suitably passed through the means 10 or not. When the beam L is not suitably passed through the means 10, a control part 25 controls a piezo element 24 and adjusts the angle of the mirror 23 to adjust the incident angle of the beam L upon the means 10. When the beam L is suitably passed through the means 10, the side lobe of the beam L is cut out by a slit 13 to shape the beam.