The speed of the laser scanned with the scanning means such as a galvanometer mirror or the polygon mirror is not constant in the center portion and in the end portion of the scanning width. As a result, the object to be irradiated is irradiated with the excessive energy and thereby there is a risk that the amorphous semiconductor film may be peeled.In the case of scanning the spot of the energy beam output continuously with the scanning means, the present invention is to block the CW beam irradiated to the regions in the object to be irradiated where the scanning speed of the spot accelerates, decelerates, and it becomes zero, that is to say, when the spot is in the position where the scanning starts and in the position where the scanning ends.