A sliding bearing 1 includes: a synthetic resin-made upper casing 2 which is fixed to a vehicle body side via a mounting member; a synthetic resin-made lower casing 3 which is superposed on the upper casing 2 and on which a spring bearing surface for a suspension coil spring is formed; a synthetic resin-made sliding bearing piece 5 disposed in an annular space 4 between the upper casing 2 and the lower casing 3; and an annular inner seal member 8 and an annular outer seal member 9, both made of a synthetic resin, for respectively sealing an annular gap 6 on an inner peripheral side in a radial direction X and an annular gap 7 on an outer peripheral side in the radial direction X between the upper casing 2 and the lower casing 3, the annular gap 6 and the annular gap 7 allowing the annular space 4 to communicate with the outside.