Fixing device and fixing method and image forming device

A fixing device (23) comprising a fixing roller (131) in contact with a toner image surface and a pressure roller (132) in contact with the surface opposite to the toner image surface so as to fix a toner image onto a recording sheet (P) when the sheet (P) formed with a non-fixed toner image passes through a fixing nip unit (Y) in pressure contact with the fixing roller (131) and the pressure roller (132), wherein a control circuit (150) for controlling heating lamps (134-136) is provided so that the surface temperature of the pressure roller (132) falls within a temperature range specified by the low-temperature offset occurring boundary temperature (Thc) of the fixing roller (131) and/or the high-temperature offset occurring boundary temperature (Thh) of the fixing roller (131). Accordingly, the phenomenon of transferring toner to the roller pair (transfer from the rear surface of the recording sheet to the pressure roller, transfer from the pressure roller to the fixing roller) can be weakened or prevented.