PURPOSE: To form a uniform thin film on a metallic sample having a wide plane area by disposing an anode which converges plasma and generates metallic ion in a vacuum vessel in a position facing the central part of the plane of the metallic surface so that the metallic ion moves in the direction perpendicular to the plane of the metallic sample.

CONSTITUTION: A discharge electrode 2 generates a circular cylindrical plasma 4' which is drawn out by the magnetic field of a magnetic coil into a vacuum vessel 1. The plasma 4' passes through permanent magnets 6, 7, by which sheet plasma 4 is formed. Said plasma advances in a horizontal direction in the state of enclosing a plane metallic material 8 biased to negative potential and while the plasma is attracted by the magnetic field of a permanent magnet 13, the plasma is changed downward from the horizontal direction by the magnetic field of a permanent magnet 11 and is converged to an anode 10 disposed below the material 8. The metal for plating on the anode 10 to which the plasma is converged is ionized by the plasma 4 and forms a thin film on the material 8.