A fixing device includes a support member fixedly provided inside a loop formed by a fixing member to support a nip formation member provided inside the loop formed by the fixing member. A biasing member is provided between the support member and a heater support that supports a laminated heater that generates heat to be transmitted to the fixing member. The heater support thermally expands in a first direction due to heat generated by the laminated heater. The biasing member applies bias to the heater support in a second direction opposite the first direction and in which the heater support presses the laminated heater against an inner circumferential surface of the fixing member.