Abstract: An annular groove is provided to the rotary portion and/or the fixed portion in a bearing seal portion, and its cross section has a shape approximated by an arc. The annular groove is such that the relationship between the groove width W in a direction following the surface constituting a bearing seal portion and the groove depth Dg in a direction perpendicular to the surface constituting the bearing seal portion is Dg/W<0.4.

Abstract: An annular groove is provided to the rotary portion and/or the fixed portion in a bearing seal portion, and its cross section has a shape approximated by an arc. The annular groove is such that the relationship between the groove width W in a direction following the surface constituting a bearing seal portion and the groove depth Dg in a direction perpendicular to the surface constituting the bearing seal portion is Dg/W<0.4.

Abstract: To provide a hydrodynamic bearing device which can be made small and thin with a sufficient length of the radial bearing being secured, which can prevent leakage of a lubricant even when there is a significant error in shape and/or a disturbance such as a shock and the like, and also which is not affected by deformation of a hub. A radial hydrodynamic bearing is provided between an outer periphery of the shaft and an inner periphery of a sleeve, and a thrust hydrodynamic bearing is formed between a lower surface of the shaft and an upper surface of the thrust plate. Also, a seal portion is formed by an inner peripheral surface of an upper recessed portion of the sleeve, and an outer peripheral surface of a cover plate.