PURPOSE: To obtain good finish appearance and quality by wiping the surface of a substrate with a cloth such as qauze impregnated with an org. solvent to remove oil, etc. on the surface then bringing ionized air into contact with the surface and subjecting the surface to electrostatic painting.

CONSTITUTION: After the materials, such as oil, dust, dirt, and the like stuck on the surface of a substrate are removed therefrom by wiping the surface with a cloth such as gauze impregnated with an org. solvent, the surface of the substrate is brought into contact with ionized air by spraying the air which is ionized like plasma or the like; thereafter the surface is subjected to electrostatic painting, whereby the paint film of beautiful finish appearance free from ruggedness is formed. Here, the air which is ionized like plasma refers to the air wherein positive ions and negative ions exist in combination and is usually obtained by inserting a pair of needle electrodes into air, and applying the dielectric breakdown voltage of the air or the voltage larger than said voltage between the electrodes.