Disclosed herein is a semiconductor device manufacturing method for performing an annealing process of irradiating a semiconductor film on which element forming areas including thin film transistor forming areas are arranged in a two-dimensional pattern with energy beams using a plurality of irradiating optical systems, wherein in the annealing process, an area irradiated with the energy beams is divided into a single beam irradiated area irradiated by each of the plurality of irradiating optical systems with an energy beam singly and a boundary area situated between single beam irradiated areas adjacent to each other and irradiated by both of two irradiating optical systems performing beam irradiation of the single beam irradiated areas with energy beams.