A fixing device includes a fixing roller, a fixing belt which is made to rotate by a rotation force received from the fixing roller, a nip forming unit to form a nip zone at a contact area between the fixing roller and the fixing belt, and a first heating unit, which is separated from the nip zone, to apply heat to the fixing belt. The nip zone and the heating unit are separated, so that the heating unit can be prevented from being broken as a result of the pressurization and thermal deformation.