To provide a ball screw mechanism sliding resistance of which is comparatively small at low cost.

A holding member 6 mounted on a land part 1b of a screw shaft 1 holds a lubricant and can lubricate a rolling surface by the lubricant. The lubricant pushed out from the rolling surface by a ball 3 in accordance with rotation of the screw shaft 1 is held by the holding member 6 again, the replenishing frequency of the lubricant can be minimized and its maintenance property is improved. Further, it is possible to restrain the sliding resistance to save energy as only a fore end of a brush 6b is devised to make contact with an inner peripheral surface of a nut 2.