A bearing device includes a bearing portion that includes an inner ring, an outer ring, a plurality of rolling elements that are interposed between the inner ring and the outer ring, and a cage that holds the plurality of rolling elements, one of the inner ring and the outer ring being a rotational ring, and another of the inner ring and the outer ring being a fixed ring; and an oil supply unit that is provided adjacent to the bearing portion in an axial direction. The cage includes a guide portion that is configured to be in sliding contact with a part of the fixed ring via lubricating oil. The oil supply unit includes a vibration sensor configured to detect a vibration of the fixed ring, and a pump configured to supply the lubricating oil to the bearing portion.