There is provided a roller screw comprising a screw shaft 1 having an outer peripheral surface in which a spiral roller rolling groove 1a is formed, a nut member 2 having an inner peripheral surface in which a spiral loaded roller rolling groove 2a is formed so as to oppose to the roller rolling groove of the screw shaft, a return pipe 4 in which a roller return passage 5 is formed so as to connect one and another ends of a loaded roller rolling passage 3 between the roller rolling groove 1a of the screw shaft 1 and the loaded roller rolling groove 2a of the nut member 2, a number of rollers 6 disposed in the loaded roller rolling passage 3 and the roller return passage 5, wherein the roller return passage 5 is twisted so that an attitude of the roller 6 changes as the roller moves in an axial direction of the return pipe 4. Such roller screw enables to provide an easy assembling and compact structure and to realize smooth circulation of the roller.