Abstract: A cement jacket for a cemented artificial joint stem, the cement jacket including a main body with a hollow interior and an open upper end for receiving and enclosing at least a part of a stem of an artificial joint, the cement jacket being shaped and adapted for longitudinal insertion in an opening formed in a bone canal of a human body, the cement jacket being made of cement and reinforced by imbedded wire or fiber and having an inner surface coated with a plastic film having a high resistance to abrasion, and the outer surface of the cement jacket is formed with discharging paths in the longitudinal direction so that excessive cement paste previously poured into the bone canal for the surgical purpose can be easily discharged upward at the time of inserting the jacket.