A fixing device has a fixing unit and a temperature detection unit. The fixing unit includes a heat roller provided with a roller section and a heater section, and a pressure roller in pressure contact with the heat roller. These rollers are disposed in a protective cover. The roller section includes a base layer of aluminum formed into a hollow cylindrical shape, a black radiation layer, and a toner parting layer. The heater section is disposed in a hollow space of the base layer. In this heat roller, when heat is emitted from the heater section, and the heat is transmitted to the radiation layer via the base layer, greater amount of infrared radiation is emitted from the radiation layer than in the case of a heat roller that is not equipped with the radiation layer. The temperature detecting unit includes an infrared radiation sensor. Thus, even if a noise component is absorbed to some extent by locating the sensor at a distance from the heat roller on an outside of the protective cover, the temperature of the heat roller is detected accurately.