Both ends of a main shaft are fixed so as not to rotate, so a rotatable moving body can be moved along the main shaft when a screw-rotor is rotated on the main shaft and a spline-rotor does not rotate thereon. The rotatable moving body can be rotated on the main shaft when the screw-rotor and the spline-rotor rotate on the main shaft. Further, the rotatable moving body can be moved along and rotated on the main shaft when the spline-rotor rotates on the main shaft and the screw-rotor does not rotate thereon. In case that both ends of the main shaft are respectively fixed to travellers, which are capable of moving in the direction perpendicular to the axial direction of the main shaft in the same direction at the same speed, the rotatable moving body can be moved in a plane. Further, in case of a plurality of subdrive systems, a plurality of rotatable moving bodies can be moved independently.