PURPOSE: To reduce the time of ion bombardment at the time of vapor-plating a substrate while inclining and rotating the substrate by inclining and rotating the substrate even in the ion bombardment as the pretreatment and specifying the inclination of the substrate.
CONSTITUTION: The surface of the inorg. substrate 1 having a through hole and the inner periphery of the through hole are vapor-plated to form a thin-film metal layer. In this metallization process, the substrate 1 and an electrode 16 are opposed in the atmosphere of a discharge gas. In this case, the inequality must be fulfilled, when the thickness of the substrate 1 is denoted by (t), the diameter of the through hole by (d) and the angle between the surface of the substrate 1 and that of the electrode 16 by θ. The substrate 1 is rotated on one axis parallel to the normal to its surface, a high-frequency wave is impressed between the substrate 1 and electrode 16, and ion bombardment is applied with the substrate as a target. The substrate is then vapor-plated.