A sliding bearing (1) comprises an upper case (3) having an annular lower surface (2), a lower case (5) so superposed on the upper case (3) as to be capable of rotating around the axis (O) of the upper case (3) and having an annular upper surface (4) facing the annular lower surface (2) of the upper case (3), an annular thrust sliding bearing piece (7) disposed in the annular space (6) between the annular lower surface (2) and the annular upper surface (4), a seal means (8) disposed on the outer peripheral side of the annular space (6), and a seal means (9) disposed on the inner peripheral side of the annular space (6).