An object of the present invention to provide a hydrodynamic bearing device and a motor having a high performance and reliability which prevents deterioration in a temperature property due to a difference in coefficients of linear expansion of a sleeve and a shaft and prevents abrasion of bearing surfaces of both the sleeve and the shaft. The sleeve is formed of a copper metal material or an iron metal material and is treated with electroless nickel plating at least on the surface which opposes the shaft. The shaft includes 0.2% by weight C, 0.3% by weight Si, 8% by weight Mn, 0.2% by weight S, 2.5% by weight Ni, and 14% by weight Cr, and a main component of the shaft is a manganese alloy steel including Fe.