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 in a circumferential direction relative to said upper casing, and a synthetic resin-made sliding bearing piece disposed between said upper casing and said lower casing, wherein said upper casing includes: an annular upper casing base portion having an annular lower surface in a vertical direction; an inner peripheral-side cylindrical suspended portion suspended from a radial inner peripheral end portion of the upper casing base portion; an outer peripheral-side cylindrical suspended portion suspended from a radial outer peripheral end portion of the upper casing base portion; and an engaging bulged portion provided on a lower portion of a cylindrical inner peripheral surface of the outer peripheral-side cylindrical suspended portion, characterized in that said lower casing includes: an annular lower casing base portion having an annular upper surface in the vertical direction; a cylindrical protruding portion which protrudes downwardly from an annular lower surface of the lower casing base portion and has a cylindrical inner peripheral surface continuously connected to a cylindrical inner peripheral surface of the lower casing base portion; an annular protruding portion which protrudes upwardly from the annular upper surface of the lower casing base portion; an inner peripheral-side annular upright wall portion and an outer peripheral-side annular upright wall portion which protrude upwardly from an annular upper surface of the annular protruding portion so as to form on the annular upper surface of the annular protruding portion an annular recessed portion in cooperation with the annular upper surface; an annular collar portion which protrudes radially outwardly from a lower end portion of a cylindrical outer peripheral surface of the annular protruding portion; at least one projecting portion which projects radially outwardly from the cylindrical outer peripheral surface of the annular protruding portion between an annular upper surface of the annular protruding portion and the annular collar portion in the vertical direction; and an annular plate-like portion protruding radially outwardly from a lower end portion of a cylindrical outer peripheral surface of the lower casing base portion, wherein said sliding bearing piece includes: an annular thrust sliding bearing piece portion having an annular upper surface and an annular lower surface in the vertical direction; an annular connecting piece portion extending radially outwardly from an outer peripheral end portion of the thrust sliding bearing piece portion and having an annular upper surface continuously connected to the annular upper surface; a radial sliding bearing piece portion which is suspended from an outer peripheral end portion of the annular connecting piece portion and has a cylindrical inner peripheral surface and a cylindrical outer peripheral surface; and a corrugated meshing portion in which projecting portions and indented portions are alternately formed along the circumferential direction on the cylindrical inner peripheral surface of the radial sliding bearing piece portion, said sliding bearing piece being disposed between said upper casing and said lower casing such that the thrust sliding bearing piece portion is fittingly inserted into the annular recessed portion of said lower casing and such that the cylindrical inner peripheral surface of the radial sliding bearing piece portion is brought into contact with cylindrical outer peripheral surfaces of the outer peripheral-side annular upright wall portion and the annular protruding portion and the indented portion of the corrugated meshing portion is meshed with the projecting portion so as to inhibit the rotation of said sliding bearing piece about the axis with respect to said lower casing, said upper casing being combined with said lower casing such that the annular lower surface of the upper casing base portion is brought into slidable contact with the annular upper surface of the thrust sliding bearing piece portion, and the cylindrical inner peripheral surface of the outer peripheral-side cylindrical suspended portion is brought into slidable contact with the cylindrical outer peripheral surface of the radial sliding bearing piece portion, and such that the engaging bulged portion is resiliently fitted to the annular collar portion of said lower casing.