To realize high quality for a semiconductor thin film used in the active layer of a thin-film transistor.

In order to manufacture a thin-film transistor, first a film-forming process is performed, and a semiconductor thin film is formed on the surface of an insulating substrate 0 stretching in the longitudinal direction and in the width direction which are rectangular to each other. Secondly, an annealing process is performed, and the semiconductor thin film is modified by applying energy from the outside. A working process is performed, and a thin-film transistor is formed by making the modified semiconductor thin film an active layer. In the annealing process, the semiconductor thin film is intermittently irradiated with a laser light 50 of comparatively high energy, which is rectangularly shaped along the width direction of the insulating substrate 0, and is irradiated, and meanwhile intermittently and almost synchronously with the irradiation timing of the laser light 50, and meanwhile it is irradiated with a lamp light of comparatively low energy which is linearly formed along the substrate 0 by using a pair of upper and lower arc lamps 61, 62. The insulating substrate 0 is transferred in the longitudinal direction, synchronously with the irradiation timing.