A fixing device may include: a roller; a heating assembly; a pressing assembly; and a frame. The heating assembly may include a guided portion having first and second surfaces. The frame may movably support the heating assembly. The frame may include: a recessed portion; first and second guide portions. The first and second guide portions may guide movement of the heating assembly. The guided portion may be interposed between the first and second guide portions. The first guide portion may have a first restriction surface facing the first surface to restrict the guided portion from moving. The second guide portion may have a second restriction surface facing the second surface to restrict the guided portion from moving. Farthest end portions of the first and second restriction surfaces to the roller may face the first and second surfaces respectively when the heating assembly is in its closest position to the roller.