To prevent toner from melt-sticking on each developing sleeve surface by suppressing the temperature rise caused by toner rubbing the surfaces of developing sleeves arranged adjacent and opposite to each other.

By rotating the 1st sleeve 12 positioned on the upstream side of the photoreceptor drum 1 in the rotating direction and the 2nd sleeve 13 positioned on the downstream side of the photoreceptor drum 1 in the rotating direction, respectively, while controlling the circumferential velocity of the 1st sleeve to be higher than that of the 2nd sleeve 13, the drastic rubbing of the toner near a part (gap part N) where both rollers come adjacent and opposite to each other is mitigated, and each temperature rise of the 1st sleeve 12 and the 2nd sleeve 13 is suppressed, then, the toner is prevented from melt- sticking.