According to an embodiment, provided is a fixing device that includes: a rotatable fixing member that heats a recording medium on a side carrying an unfixed image; a rotatable pressing member that is pressed and is contacted with the fixing member to form a nip portion between the pressing member and the fixing member; a heat source heating the fixing member; a relay switch provided in an energizing path for the heat source; a temperature detection sensor detecting a temperature of the fixing member; and a control unit that controls energization of the heat source according to the temperature detected by the temperature detection sensor. The control unit keeps the relay switch in an off state if the temperature of the fixing member is equal to or more than a predetermined temperature when the fixing member has stopped rotation.