To provide a means for heightening dust proof performance while moderately keeping sliding resistance of a sealing body of a ball screw device.

This ball screw device includes: a screw shaft provided with a spiral shaft raceway groove formed on the outer peripheral surface; a nut provided with a nut raceway groove formed opposite to the shaft raceway groove on the inner peripheral surface; and a contact type sealing body disposed at the front and rear ends of the nut. The shaft raceway groove and the nut raceway groove are screwed via a plurality of balls. A groove sliding contact part brought into sliding contact with the shaft raceway groove is provided in the sealing body, and a substantially circular-arc sealing piece is formed on the side brought into sliding contact with the circular-arc surface of the shaft raceway groove of the groove sliding contact part.