To provide a dynamic pressure bearing device which does not leak an encapsulated lubricating fluid in the case of an increase in temperature of a device to elongate the life time thereof.

A lid member 3 which is fitted into a circumferential shoulder 1a which is provided to the opening at one end of a sleeve 1 is formed from a material with a larger linear coefficient of expansion than that of the material which constructs the sleeve 1. This construction provides the dynamic pressure bearing device with a bearing gap S1 on the sealing end side of the sleeve 1 larger than a bearing gap S2 on the open end side thereof. Depending on the shape of the circumferential surface 1a of the sleeve, the lubricating fluid between the sleeve 1 and a shaft 2 is pushed from the open end of the sleeve 1 toward the sealing end thereof according to relative rotation between them. Thus, the dynamic pressure bearing device according to the present invention can prevent the lubricating fluid from leaking from the open end of the sleeve when operation is carried out under a high temperature environment or when the temperature of the lubricating fluid is increased due to prolonged rotation.