To prevent lubricating fluid from leaking to the outside of a device by thermal expansion without increasing a volume of a taper seal portion, in a dynamic pressure bearing device having structure of a minute gap between a shaft member and a sleeve member, totally filled with lubricating fluid.

This device includes a shaft member 11 having a shaft portion 111 and a thrust plate portion 112, a sleeve member 12 made of a porous sintered body, placed opposedly against the shaft portion 111 with a minute gap, a sleeve support member 13 supporting the sleeve member 12, a thrust bush member 14 placed opposedly against a lower surface of the plate portion 112 with a minute gap, sealing a lower opening of the member 13, and lubricating fluid filled in the whole minute gap. An expansion member B1 having the negative thermal expansion coefficient is attached to locations other than a location that is in contact with the lubricating fluid and that is a groove for generating dynamic pressure, in at least on a member of the shaft member 11, the sleeve member 12, the support member 13 and the member 14.