To provide a ball screw device in which dynamic friction torque hardly increases even when a nut is contracted by cooling.

This ball screw device includes a screw shaft 10, a nut 20 screwed to the screw shaft 10 through a plurality of rolling elements 30, and a cooling structure 40 to cool the nut 20, wherein the plurality of rolling elements 30 each provided with a pre-load in a two-point contact state by using a pre-load direction as a tensile direction are incorporated between a thread groove 10a of the screw shaft 10 and a thread groove 20a of the nut 20. Circulation paths 21c, 22c and a second through-hole 52 are formed in the nuts 21, 22 and a spacer 50, and a cooling medium is supplied to them to form a cooling structure. A sealing structure 70 is arranged between the circulation paths 21c, 22c and the second through-hole 52. The cooling through-holes 20b, 20c, a tube 4, a cooling liquid introduction pipe 5 and a cooling liquid discharge pipe 6 have shapes and areas of the respective passage cross-sectional surfaces identical to or nearly identical to one another, and they are connected in series to one another.