Rolling bearings are stacked with their center lines extending in a vertical direction. Each of the rolling bearings has an inner ring, an outer ring, a plurality of balls, and an annular cage. Each of the rolling bearings has a structure that induces, upon rotation, an action that causes lubricating oil to flow upward along the outer ring in the annular space. The cage has an annular portion provided adjacently below the balls to prevent air from moving to the outer ring side from the inner ring side.