Using an operation panel a user selects group to which a recording medium to be subjected to image formation belongs out of plural groups of recording media classified according to grammages, a classification processing unit sub-classifies the group selected, to which the recording medium belongs, into plural sub-groups of recording media according to a detecting result of the media sensor provided further upstream in a conveying direction of a recording medium than a fixing unit, and a control unit sets, for the recording medium belonging to the group selected, the temperature of the fixing unit to a fixing temperature in a fixing temperature range and controls this fixing temperature according to any one of the sub-groups sub-classified. Consequently, it is possible to perform fixing processing at an optimum temperature according to a type of a recording medium.