A fixer (heater) includes a heat roller and a pressure roller pressing each other. The fixer heats a heated material by passing the heated material through a press region where the heat roller and the pressure roller meet. The fixer further includes an external heat roller heating the pressure roller from outside the pressure roller. A transit time taken for any given point on the heated material to pass through the press region is less than or equal to 2.3.times.10.sup.-2 sec. The surface temperature, T1 (.degree. C.), of the heat roller and the surface temperature, T2 (.degree. C.), of the pressure roller satisfy T1-T2.ltoreq.100 (.degree. C.), and preferably satisfy T1-T2.ltoreq.70 (.degree. C.). The load on the heat roller is reduced, and so is the power consumption.