A laser annealing device includes: a CW laser device configured to emit continuous wave laser light caused by continuous oscillation to preheat the amorphous silicon; a pulse laser device configured to emit the pulse laser light toward the preheated amorphous silicon; an optical system configured to guide the continuous wave laser light and the pulse laser light to the amorphous silicon; and a control unit configured to control an irradiation energy density of the continuous wave laser light so as to preheat the amorphous silicon to have a predetermined target temperature less than a melting point thereof, and configured to control at least one of a fluence and a number of pulses of the pulse laser light so as to crystallize the preheated amorphous silicon.