To provide a fixing device improved in fixation of an annular member to a cylindrical member. The fixing device for fixing the annular member to the cylindrical member that includes a first fixing portion and a second fixing portion. The first fixing portion includes an annular portion and an adjustment portion. The annular portion covers an outer peripheral surface of the cylindrical member from outward in a radial direction. A circumferential length of the annular portion is adjustable with the adjustment portion. The second fixing portion is fixed to the first fixing portion and fixed to the annular member.