Floating bush bearing device and supercharger

A floating bush bearing configured to support a rotational shaft rotatably includes: a floating bush body part formed to have a cylindrical shape having an insertion hole through which the rotational shaft is inserted. The floating bush body part includes: an inner peripheral surface; an outer peripheral surface having a greater width dimension than the inner peripheral surface in an axial direction of the floating bush body part; and an axial end surface which connects an end of the inner peripheral surface and an end of the outer peripheral surface, the axial end surface including a vertical surface extending along a direction orthogonal to the axial direction from the end of the outer peripheral surface toward a radially inner side and an oblique surface extending from a radially inner end of the vertical surface toward the end of the inner peripheral surface. The oblique surface has a protruding portion protruding from a virtual line which linearly connects the radially inner end of the vertical surface and the end of the inner peripheral surface.