<p>An improved spindle drive mechanism (5) for a machine tool has a screw shaft (11) having formed on its outer peripheral surface a helical screw groove (11a); a ball screw nut (12) having formed on its inner peripheral surface a helical nut groove corresponding to the screw groove (11a) and adapted to be reciprocable in the direction of the axis of the screw shaft (11) as the screw shaft (11) rotates about its axis; a hollow motor (21) constructed from a circular tube-like inner rotor (22) and a circular tube-like outer stator (23), the circular tube-like inner rotor (22) being fixed on the outer peripheral surface of the ball screw nut (12) and functioning as a field flux generation source, the circular tube-like outer stator (23) generating a rotating field for applying rotational driving force to the inner rotor (22); a tubular casing (31) having one end to which the outer stator (23) is fixed and the other end to which a spindle (51) for the machine tool is fixed; and an outer tube (41) for guiding reciprocation of the casing (31) in the direction of its axis.</p>
