3 in fig1 the speed of the photosensitive drums when driven in common by the dc motor and the speed v 1 in fig6 the speed of the photosensitive drums when individually driven by the ultrasonic motor are shown in fig8 a and 8b in fig8 a the fluctuation for each one full rotation of the photosensitive drum is not seen whereas in fig8 b the fluctuation for each one full rotation of the photosensitive drum appears clearly that is it is seen that when the photosensitive drums are individually driven by the ultrasonic motor the fluctuation for each one full rotation of the photosensitive drum is controlled and decreased as compared with the case where the photosensitive drums are driven in common by the dc motor as is apparent from the foregoing description in the image forming apparatus of the present invention a drive source for individually and directly driving each image bearing member is disposed near each image bearing member the drive source has detecting means for receiving a load in a rotation generating portion and detecting the rotated state of the rotary output shaft thereof and the rotation of the rotary output shaft is controlled on the basis of the detection signal of the detecting means therefore the speed controlling function of the drive source can effectively make the image bearing members work and the fluctuation of the image for each one full rotation of the image bearing members can be suppressed accordingly images of high quality free of any fluctuation in images can be obtained also during the assemblage of the.