A rolling bearing unit includes: an inner ring member having a recess on a first side in an axial direction, the recess being recessed toward a second side in the axial direction; an outer ring member disposed on the outer periphery side of the inner ring member; a rolling body disposed between the inner ring member and the outer ring member and rotatably supporting the inner ring member with respect to the outer ring member; a transmitter capable of transmitting at least one of electric power or a signal, at least a part of the transmitter being accommodated inside the recess of the inner ring member; and a covering member that is supported by the first side of the outer ring member in the axial direction, covers the first side of the inner ring member in the axial direction, and fixes the transmitter.