A fluid dynamic-pressure bearing includes a rotatable shaft, a hub, a
fixed portion, and a lubricating liquid. The hub includes a hub thrust
bearing surface extending from the shaft outwardly in a radial direction
and an annular surface. The fixed portion includes a fixed-portion upper
thrust bearing surface facing the hub thrust surface and a flange surface
facing the annular surface. The hub thrust bearing surface, the
fixed-portion upper thrust bearing surface, and the lubricating liquid
arranged therebetween form together an upper thrust dynamic-pressure
bearing. The annular surface and the flange surface define an annular gap
therebetween. An axial dimension of the annular gap is larger than a
total of an axial dimension of an upper thrust gap between the hub thrust
bearing surface and the fixed-portion upper thrust bearing surface and an
average depth of upper thrust dynamic-pressure generating grooves of the
upper thrust dynamic-pressure bearing.