phenomena due to the pressure difference thereby spouting out in the second vacuum chamber 106 from the oil injecting opening 108 in case where the fluid dynamic pressure bearing 10 is applied as a bearing device for a motor in a hard disk drive device or the like used under a clean environment the spouting oill kept to be adhered pollutes the clean environment therefore it is required to wipe the inside of the second vacuum chamber 106 or the surface of the fluid dynamic pressure bearing 10 moreover in case where the bubbling phenomena is caused in the pipe 112 the oill is broken by the air bubbles in the pipe 112 so that the oill cannot smoothly be supplied toward the oil injecting opening 108 these problems cause a serious reduction in productivity of the fluid dynamic pressure bearing 10 on the other hand the relationship of pl 1 gt pl 3 is established between the reduced pressure level pl 1 in the first vacuum chamber 100 and the reduced pressure level pl 3 in the second vacuum chamber whereby the oill is transported toward the side where the pressure is higher the degree of vacuum is lower successively during the oil filling process thereby being capable of surely preventing the occurrence of bubbling phenomena in this case the pressure in the second vacuum chamber 106 wherein.