A pressure inside a chamber in which a bearing is arranged is reduced. Thus, a pressure inside an oil tank and the pressure inside the chamber are made lower than atmospheric pressure, and are placed in a minimal or no pressure difference condition. Next, a lubricating oil is supplied from the oil tank into the chamber through power of a liquid transfer pump. The lubricating oil is thus injected into the bearing inside the chamber. Thus, the lubricating oil can be supplied from the oil tank into the chamber while maintaining the pressure at substantially the same level lower than that of the atmospheric pressure. Accordingly, gas can be prevented from dissolving into the lubricating oil which has once been deaerated by a pressure reduction inside the oil tank. In addition, because a driving force of the liquid transfer pump is used for supply of the lubricating oil, it is easy to control the amount of the lubricating oil to be supplied.