There is provided a hydrodynamic bearing assembly including: a shaft; a sleeve disposed to be spaced apart from the shaft by a predetermined interval to form a bearing clearance therewith; and a thrust member installed on the shaft, wherein at least one of the shaft, the sleeve, and the thrust member is provided with a dynamic pressure groove for generating fluid dynamic pressure in a lubricating fluid provided in the bearing clearance, and one side of a portion of the dynamic pressure groove into which the lubricating fluid is introduced is provided with a pressure reduction preventing groove for suppressing a reduction in pressure generated at the time of introduction of the lubricating fluid.