A heating device including a heater; a flange including a beam, wherein the flange rotatably supports an endless belt; a temperature detector to detect a temperature, the temperature detector disposed inside the endless belt; a lead wire connected to the temperature detector, the lead wire extending from an inside of the endless belt to an outside of the endless belt through an inside of the flange, wherein the inside of the flange is a side surrounded by the beam and the other surface of the flange; a heater holder to hold the heater; and a gap separates the flange from one of the heater, the heater holder, and a stay, when all of the heater, the heater holder, and the stay were pressed toward one side of the flange, and the gap is smaller than a diameter of the lead wire.