PURPOSE: To reduce the amt. of the material to be vapor-deposited on the inside of a laser beam incident window and to improve the utilizing efficiency of the machine by providing a laser beam shielding plate at a position through which a laser beam condensed in the vacuum chamber of a laser-beam machine passes.

CONSTITUTION: A laser beam 7 generated from a laser 1 such as an excimer laser is condensed by a lens 2 and introduced into a vacuum chamber 6 through an incident window 3, hence a target 4 is irradiated with the beam 7, heated and vaporized, and the vaporized material 8 of the target is deposited on a substrate 5 as a thin film. In this case, the vapor-deposited material from the target 4 is also deposited on the inside of the window 3 to reduce the transmittance of the beam 7, hence the reproducibility of the characteristic of the thin film on the substrate 5 is deteriorated, and the deposit on the inside of the window 3 has to be frequently cleaned off. Accordingly, a shielding plate 9 having a small hole 9a for passing the beam 7 is provided at the condensed beam 7 part to drastically reduce the amt. of the deposit on the inside of the window.