PURPOSE: To improve adhesion of a vapor deposition film and to increase the anode capacitance of an electrolytic capacitor by attaching tantalum on the surface of an electrode comprising high purity aluminum by a cathode arc vapor deposition method, and forming the vapor deposition film of the tantalum layer.

CONSTITUTION: A tantalum target 10 is used as a cathode and arc discharging is performed in a vacuum state. Then, an arc spot is formed on the surface of the target by the arcing. The arc randomly runs around on the surface of the target. The target 10 is instantaneously fused and evaporated by the arc current which is concentrated on the spot. At the same time, metal ions 12 are formed and discharged into the vacuum. A bias voltage is applied on a material to be coated 14 comprising high purity aluminum. Then, the metal ions and accelerated reaction gas particles 16 are attached on the material to be coated 14 together. Thus, a vapor deposition film is grown. In this way, adhesion between the aluminum electrode and the tantalum is improved, and the anode capacitance of an electrolytic capacitor is increased.