A rotary developing device which facilitates a positional adjustment of developing units and prevents the developing units from being shifted even when they are used for a long period. Pins protruding from a revolver are inserted into elongated holes formed in developing units so that developing units are held in such a manner that the developing units are movable relative to the revolver. By mounting a spacer between the elongated hole and the pin, the positional adjustment of the photosensitive drum and the tracking roller is completed. Furthermore, a plurality of spacers which differ in thickness are prepared and by merely selectively mounting an appropriate spacer, the position adjustment of the tracking roller is completed.