A heating fixer, including a fixing member heating and melting a toner image; a pressure member contacting the fixing member upon application of pressure to form a nip; a variable device varying the pressure of the pressure member to the fixing member with rotation of a cam to vary a width of the nip into at least three steps; a drive motor driving the cam; and at least two position detectors detecting a rotational position of the cam, wherein each of the position detectors is formed of a fixed transmission sensor and a blocking filler coaxially rotating with the cam in a body, the blocking filler includes a blocking blade capable of blocking light received by the transmission sensor, the plural blocking fillers include blocking blades so as to have phases different from each other among the blocking fillers.