(1) 2.4???103???d/(TC???t)<T0, where d is a thickness of the unfixed toner layer in meters, TC is a thermal conductivity of toner in W/mK, and t is the fixing time in seconds, (2) a temperature Ttop of a topmost layer of the toner layer is not greater than the minimum temperature TOFF at which the hot offset of the surface of the first fixing member occurs when the fixing time is set to 1 seconds,