To enable uniform working for an object to be machined and also to increase the machining speed by dividing one laser beam into plural beams to form a line of parallel beams, converging such beams for multiple reflection, synthesizing them into one linear beam, and reducing it for image-forming on the object to be machined.

One laser beam 21 is divided into four beams for example to form a line of parallel beams 22-25. These parallel beams 22-25 are passed through a converging means (RO), multiple-reflected and synthesized into one linear beam 26. The linear beam 26 is reduction image-formed on an object 28 to be machined, as a linear beam 27 by a reduction image-forming means (NI). This linear beam 27 is a top flat beam whose energy intensity distribution is uniformized in the beam cross section; therefore, using this beam, an amorphous silicon film or the like can be uniformly etched, with the machining speed greatly increased in comparison with a conventional circular beam.