PURPOSE: To efficiently prepare carbon minute particles having a specific size or less by roughly grinding a carbon fiber by a ball mill and finely grinding the roughly ground carbon fiber by a vibration ball mill.

CONSTITUTION: A carbon fiber is roughly ground to a size of about 1mm or less using a ball mill or a vibration rod mill and, subsequently, the roughly ground carbon fiber is finely ground to a particle size of about 10μ or less using a vibration ball mill. As a result, carbon fiber refuse can be finely ground with high efficiency incapable of being expected heretofore and the reutilization of the carbon fiber refuse becomes possible on an industrial scale for the first time. Since the particle diameter of the final product becomes 10μ or less, even when the obtained particles are used as the additive of paint, the surface of a film does not become rough and aesthetic appearance is not damaged.