The present invention relates to a laser processing method and laser processing apparatus for enabling improvement and maintenance of homogenization of a beam intensity distribution in an irradiated region. The upper plate overlies the lower plate and includes radially extending gas passages which extend inwardly from an outer periphery of the upper plate, axially extending gas passages in fluid communication with the radially extending gas passages and an annular recess forming a plenum between the upper and lower plates. Above the guide deck, a plurality of parallel belts are positioned to provide a driving force for sheets on the deck.