A fixing device of the invention detects a temperature of plural positions of a heat roller by a multiple non-contact temperature sensor at the same time and controls the temperature of plural heat source members. The non-contact temperature sensor and a contact temperature sensor detect the temperature of the same position. According to the detection result, maintenance is performed or a temperature conversion table is corrected, the non-contact temperature sensor is maintained with high precision, and the heat roller is controlled the temperature with high precision.