PURPOSE: To permit easy changing of a focusing point and working under different defocusing conditions in lens-condensed laser working by inserting a parallel glass plate having a suitable thickness between a lens and an object to be worked perpendicularly to the optical axis.

CONSTITUTION: The change of a focusing point in the case of condensing laser light 5 with a lens 6 and irradiating said light to an object 7 to be worked is accomplished by inserting a parallel glass plate 9 having a suitable thickness between the lens 6 and the work 7 perpendicularly to the optical axis. The focusing point is easily changed by inserting mechanically said plate from the side without changing the height of the lens 6 or the position of the object 7 as in the prior art. The changing position of the focusing point is selected by the thickness of the glass to be inserted.