A fixing device is disclosed, including: a fixing rotative body, a heat source, and a control part. The control part conducts a printing temperature control which varies an ON ratio per unit time of the heat source based on a detection result of the temperature detecting part to maintain a printing target temperature in a printing state, conducts a waiting temperature control which performs an ON/OFF control based on the detection result of the temperature detecting part to maintain a waiting target temperature in a waiting state after a printing operation ends, and conducts a forcible ON control which forcibly turns on the heat source for a predetermined time before starting the ON/OFF control when the detection result of the temperature detecting part after the printing operation ends is lower than the waiting target temperature.