A fixing unit, and an image forming apparatus having the fixing unit. The fixing unit includes a heat roller including a heat source therein, one or more pressing rollers in close contact with the heat roller, an elastic body to elastically apply pressure on both ends of the one or more pressing rollers with respect to the heat roller, a backup member to contact a central portion of the one or more pressing rollers and to apply pressure to the central portion in a longitudinal direction of the one or more pressing rollers, and a backup elastic body to elastically press the backup member towards the heat roller.