Oil which will serve as a lubricating fluid of a fluid dynamic pressure bearing is degassed in a first environment under a first pressure which is lower than atmospheric pressure. First and second members of the bearing are place in a second environment under a pressure lower than atmospheric pressure and higher than the pressure in the first environment. The degassed oil is supplied to the gap between bearing surfaces of the first and second members while the first and second members are in the second environment under pressure lower than atmospheric pressure and higher than the pressure in the first environment. Subsequently the pressure in the second environment is increased to force the oil into the gap between the bearing surfaces of the first and second members of the hydrodynamic fluid.