A laser processing apparatus for performing processing such as perforation on a ceramic green sheet etc. using a laser beam efficiently. The laser processing apparatus is provided with a plurality of optical path systems disposed between a laser oscillator and an irradiation position control optical system for irradiating a predetermined position on a work piece with a laser beam. The plurality of optical path systems includes an optical path system that guides the laser beam to the irradiation position control optical system without changing its cross sectional shape in the direction perpendicular to the optical axis of the laser beam and an optical path system that guides the laser beam while changing its cross sectional shape so that these optical path systems are selectively used in accordance with the processing condition.