A burden of exchanging ejector rods is reduced in an injection molding machine when exchanging rods during exchange of a die. A plurality of rod insertion holes are formed so as to pierce through a movable platen. A plurality of ejector rods are inserted into rod insertion holes so as to slide freely therein. An ejector plate is disposed at the rear side of the movable platen. In a plurality of the ejector rods, a plurality of base rods are inserted into rod insertion holes so as to slide freely therein. Their base end portions are fixed to the ejector plate. Detachable rods are removably stuck with magnetism to the base rods by first and second magnets.