PURPOSE: To execute the marking of a large area with one set of a transmitter by providing a deflector for deflecting a laser optical axis and a prism on the pulse laser beam incident side of a marking pattern mask.

CONSTITUTION: A laser beam 2 outputted from a pulse laser transmitter 1 is expanded by beam shaping parts 3, 4, and also, shaped to long elliptical shape, and irradiates a deflector 6 by a reflecting mirror 5. From the deflector 6 to a prism 7, a first laser pulse P1 and a second laser pulse P2 are deflected at a swing angle 2θS and irradiates the prism 7. A mask 8 for forming a marking pattern is provided behind the prism 7, and the laser pulse which transmits through the mask 8 passes through a light shielding plate 11 and brought to image formation on the surface of an object 10 to be worked by an image forming optical system 9, respectively and marking is executed. In such a manner, even with the irradiation of plural pulse lasers, a laser irradiation area is not superposed on the surface to be worked, and the marking of a uniform contrast can be obtained.