PURPOSE: To provide an image forming device capable of preventing the step-out or surely attaining the restarting of a stepping motor at the time of exerting the factor of load fluctuation, etc., on the rotating body driven by the stepping motor while holding the respective developing means.

CONSTITUTION: The multicolor image forming device is provided with the rotary type developing means changeover mechanism 108 by which one of the plural developing means Dc, Dm, Db and Dy is rotationally moved to the position opposite to the image carrier C by the stepping motor for properly performing the selective changeover, and moreover, the device is provided with the deviation calculating means for calculating the theoretical rotating position by the motor calculating on the basis of the drive command pulse signal of the stepping motor, the actual rotating position obtained by the actual rotating position detecting means provided to the stepping motor or the developing means changeover mechanism 108 and the deviation between the actual rotating position and the logical rotating position.