The color image forming machine such like a color printer or a color copier for forming a color image on a recording sheet. The image forming machine includes a photoreceptor belt; a belt driver for rotating the photoreceptor in a longitudinal direction; a laser beam scanner for repeatedly scanning the photoreceptor in a direction perpendicular to the longitudinal direction, with the laser beam, so that the latent image is formed on the photoreceptor; a developer for developing the latent image with plural color toners; a measuring unit for determining a rotation time of the photoreceptor; and a controller unit for controlling a scanning frequency of the laser beam scanner so that one scanning time of the laser beam scanner is set to the result of dividing the rotation time of the photoreceptor, while the photoreceptor rotates one round, by an integer.