A fixing device includes a housing, a cylindrical rotary member, a shaft, a heat source, a bearing and a ring member. The bearing includes an inner race supporting the shaft, and an outer race supporting an inner circumferential portion of the rotary member and being rotatable relatively to the inner race. The ring member is fit on the shaft adjacent to the bearing. The ring member includes an outer circumferential surface that contacts with the inner circumferential portion of the rotary member from radially inside, and a side surface that contacts the inner race and the outer race of the bearing in an axial direction.