An image forming apparatus comprising: a fixing device configured to thermally fix an unfixed image on a recording sheet by causing the recording sheet with the unfixed image formed thereon to pass through a nip formed by a pressing member pressing against an outer circumferential surface of a heating rotating body that has a resistance heating layer; a temperature measuring unit configured to measure temperatures of the resistance heating layer in a plurality of measurement regions that are set by sectioning the outer circumferential surface of the heating rotating body along a rotational axis direction of the heating rotating body; and an information obtaining unit configured to obtain information indicating temperature changes in the measurement regions in one rotational period of the heating rotating body, by sampling the temperatures measured by the temperature measuring unit during rotation of the heating rotating body; characterised by: an abnormality judging unit configured to judge whether or not an abnormality has occurred in the resistance heating layer in accordance with a result of comparison of the information obtained by the information obtaining unit, the comparison being made between measurement regions in a plurality of combinations of measurement regions wherein the plurality of combinations of measurement regions comprise the plurality of combinations of measurement regions comprising all measurement regions of a paper-passing region in the nip and at least the plurality of combinations of measurement regions comprising all measurement regions of a non-paper-passing region in the nip, wherein each combination of measurement regions is a pair of measurement regions. a fixing device configured to thermally fix an unfixed image on a recording sheet by causing the recording sheet with the unfixed image formed thereon to pass through a nip formed by a pressing member pressing against an outer circumferential surface of a heating rotating body that has a resistance heating layer; a temperature measuring unit configured to measure temperatures of the resistance heating layer in a plurality of measurement regions that are set by sectioning the outer circumferential surface of the heating rotating body along a rotational axis direction of the heating rotating body; and an information obtaining unit configured to obtain information indicating temperature changes in the measurement regions in one rotational period of the heating rotating body, by sampling the temperatures measured by the temperature measuring unit during rotation of the heating rotating body; characterised by: an abnormality judging unit configured to judge whether or not an abnormality has occurred in the resistance heating layer in accordance with a result of comparison of the information obtained by the information obtaining unit, the comparison being made between measurement regions in a plurality of combinations of measurement regions wherein the plurality of combinations of measurement regions comprise the plurality of combinations of measurement regions comprising all measurement regions of a paper-passing region in the nip and at least the plurality of combinations of measurement regions comprising all measurement regions of a non-paper-passing region in the nip, wherein each combination of measurement regions is a pair of measurement regions.