thereof that can be obtained per unit of time (minute) (hereinafter referred to as CPM) is realized.
In the image forming apparatus with the above described, any advance or delay for paper to arrive at the registration rollers 56 may occur after an image has been transferred on the paper on its first side and fixed until the paper is reversed for formation of another image on its second side thereof. One of causes for such unstable movement of the paper is that the paper is conveyed only by the conveyor belt 39 after the paper is separated from the photosensitive drum 31 until it is nipped by the pair of rollers of the fixing device 38. Therefore the paper may be moved out of place forward and backwardto form an image on a second surface of the paper, on which the image has been formed on the first surface thereof by the image formation section; after an image has been sequentially formed on the first surfaces of a predetermined number of sheets of the paper by the image formation section, the sheets of paper being reversibly conveyed and circulatorily conveyed to the second paper supply means by the circulatory conveyance means, and then image being successively formed on the second surfaces of the paper, on which the image has been formed on the first surfaces thereof; wherein a position at which the paper, on which the image has been formed on the first surface thereof, is accelerated from the paper conveyance speed during image formation