A fluid bearing device (50B, 50AB) is composed of a shaft (1, 51); a sleeve (9, 59) into which the shaft (1, 51) is inserted; and lubrication fluid (20) intervening in a gap between the shaft (1, 51) and the sleeve (9, 59), the fluid bearing device (50B, 50AB) supporting the shaft (1, 51) so as to be relatively rotatable freely with respect to the sleeve (9, 59), wherein an end portion of the sleeve (9, 59) is provided with a taper ring (4, 54) in annular shape, wherein at least either one of an inner circumferential surface (4a, 54a) of the taper ring (4, 54) and an outer circumferential surface (1a, 91b) of the shaft (1, 51) facing towards the inner circumferential surface (4a, 54a) of the taper ring (4, 54) is formed into a tapered surface (4a, 54a), which inclines in a direction as a gap between the inner circumferential surface (4a, 54a) of the taper ring (4, 54) and the outer circumferential surface (1a, 91b) of the shaft (1, 51) widens in accordance with leaving from the sleeve (9, 59) and forms a taper seal section (50TS, 50ATS) that prevents the lubrication fluid (20) from leaking out, and wherein the taper ring (4, 54) is formed by a material having coefficient of thermal expansion larger than that of the sleeve (9, 59) and the shaft (1, 51).