To reduce the damage of a ball for pinball game, and suppress the volume reduction due to wear by coating the surface of the ball for pinball game with a resin.

Balls for pinball game which have been used for a certain period of time, are washed by ultrasonic waves by placing them in a container in which a solvent such as acetone, is placed. After drying them, the balls are moved in a passage made of teflon, etc., for resin application, while making them rotate, and a thermosetting resin 3 is jetted to the balls several times, and a thin and uniform film is formed, and the film is hardened in a drying oven. By doing so, the resin 3 enters flaws K and fine unevennesses P on the surface of the balls 1 for pinball game. Also, by the thermally hardened resin 3, the surface of the ball 1 for pinball game becomes hard and smooth, and the elasticity becomes higher than that of a metal being used. Therefore, flaws become hard to generate by collisions between the balls 1 for pinball game with each other, or between the balls 1 and nails, and wear can be suppressed.