A synthetic resin-made sliding bearing comprising: a synthetic resin-made upper casing, a reinforced synthetic resin-made lower casing superposed on said upper casing so as to be rotatable about an axis relative to said upper casing, and a synthetic resin-made sliding bearing piece disposed between said upper casing and said lower casing, characterized in that said upper casing includes: an annular upper casing base portion; an inner cylindrical suspended portion which has a first cylindrical outer peripheral surface continuously connected to an annular lower surface of the upper casing base portion and is suspended from an inner edge portion of the annular lower surface of the upper casing base portion; a cylindrical engaging suspended portion which is suspended from an outer edge portion of the annular lower surface of the upper casing base portion and has an engaging bulged portion at a lower portion of a first cylindrical inner peripheral surface continuously connected to the annular lower surface of the upper casing base portion; and an outer cylindrical suspended portion suspended from the annular lower surface of the upper casing base portion so as to form a first cylindrical recessed portion in cooperation with the cylindrical engaging suspended portion and the upper casing base portion, wherein said lower casing includes: an annular lower casing base portion; a corrugated meshing portion which is formed with first projecting portions and indented portions and alternately arranged on an annular upper surface of the lower casing base portion along a circumferential direction about the axis; a cylindrical protrusion protruding from the annular upper surface of the lower casing base portion; and a cylindrical engaged protruding portion having an engaged bulged portion on an upper portion of a second cylindrical outer peripheral surface and projecting from an outer edge portion of the annular upper surface of the lower casing base portion so as to form a second cylindrical recessed portion in cooperation with the cylindrical protrusion and the lower casing base portion, and wherein said sliding bearing piece includes: a thrust sliding bearing piece portion having an annular lower surface which is brought into contact with the annular upper surface of the lower casing base portion and an annular upper surface which is slidably brought into contact with the annular lower surface of the upper casing base portion; a cylindrical radial sliding bearing piece portion suspended from an inner edge portion of the annular lower surface of the thrust sliding bearing piece portion and having a second cylindrical inner peripheral surface which is slidably brought into contact with the first cylindrical outer peripheral surface of the inner cylindrical suspended portion; and a corrugated meshed portion which is formed with second projecting portions and indented portions alternately arranged on the annular lower surface of the thrust sliding bearing piece portion along the circumferential direction about the axis, and which is meshed with the corrugated meshing portion such that the rotation about the axis relative to said lower casing is prevented by said lower casing, said upper casing being combined with said lower casing by disposing the cylindrical engaged protruding portion in the first cylindrical recessed portion, by disposing the outer cylindrical suspended portion in the second cylindrical recessed portion, and by resiliently fitting the engaging bulged portion to the engaged bulged portion.