A fusing unit is comprised of a pair of rollers, a fusing roller and a pressing roller, having an elastic layer on their outer peripheral surface and a pressing spring for pressing the fusing roller against the pressing roller, and causes a sheet of paper with an unfixed toner image to pass through the nip portion where the fusing roller and pressing roller are put in press-contact with each other so as to fuse the toner image and fix it to the paper. This fusing device further includes a roller member regulator for regulating the press-contact state when the fusing roller and pressing roller are put in press-contact with each other by the pressing spring.