Abstract: First, an axial clearance is measured. Next, lubricating oil is filled between a sleeve and a shaft, and the shaft is disposed such that a flange is positioned above a shank. Further, in a state where the shaft rotates at a rated rotation speed (a predetermined rotation speed), an axial clearance b between the flange and a surface facing a receiving surface of the flange through a flange housing space in the sleeve is measured. Finally, a dynamic pressure bearing satisfying the condition 0.3?b/a?0.55 is judged as a dynamic pressure bearing not having leakage of lubricating oil and abnormal abrasion.

Abstract: It is an object of the invention to provide a bearing device in which the bearing performance is not lowered even when the temperature is changed. In order to attain the object, the bearing device has a shaft and a sleeve. The shaft is made of stainless alloyed steel and has dynamic pressure generating grooves of a herringbone-like shape. The sleeve consists of the body made of a copper alloy, and an electroless nickel plated layer which covers the whole surface of the body. The electroless nickel plated layer has a coefficient of thermal expansion which is smaller than that of the body made of a copper alloy. The coefficient of thermal expansion of the shaft made of stainless alloyed steel is smaller than that of the body of the sleeve made of a copper alloy. When the temperature is raised, the electroless nickel plated layer suppresses the amount of thermal expansion of the body.