A thrust bearing adapted to be rotated reversibly in the normal and opposite directions comprises two flat disc elements disposed in face-to-face contact, one of the elements being provided with spiral grooves on its opposite side surfaces, one of which is reverse to the other with respect to the spiral directions, both elements having a dent formed centrally on their opposing surfaces, respectively, to form a small space in combination in which a core member of sphere is installed with a small clearance between the surfaces of the small space and the core member.