Image forming apparatus including: fixing device thermally fixing unfixed image on recording sheet by causing recording sheet to pass through nip formed by pressing member pressing against outer circumferential surface of heating rotating body having resistance heating layer; temperature measuring unit measuring temperatures of resistance heating layer in measurement regions set by sectioning outer circumferential surface of heating rotating body along rotational axis; information obtaining unit obtaining information indicating temperature changes in measurement regions in one rotational period of heating rotating body, by sampling measured temperatures; and abnormality judging unit judging whether abnormality has occurred in resistance heating layer based on result of comparison of information that is made between measurement regions in each combination, wherein one or more combinations of measurement regions have been set for each of paper-passing and non-paper-passing regions in nip by using all measurement regions in each of paper-passing and non-paper-passing regions.