In a laser processing method and a laser processing apparatus which irradiate a processing target body with a laser beam pulse-oscillated from a laser beam source, a processing state is monitored by a photodetector, and the laser beam source is again subjected to oscillation control on the moment when erroneous laser irradiation is detected, thereby performing laser processing. Further, in a laser crystallization method and a laser crystallization apparatus using a pulse-oscillated excimer laser, a homogenizing optical system, an optical element and a half mirror are arranged in an optical path, light from the half mirror is detected by a photodetector, and a light intensity insufficient irradiation position is again irradiated with a laser beam to perform crystallization when the detection value does not fall within a range of a predetermined specified value.