The present invention addresses a need to construct a synthetic-resin spinning reel spool for limiting production of sink marks on the outer surface thereof. A spinning reel spool (4) is attached onto a spool shaft (16) mounted movably back and forth in a reel unit (1) for winding a fishing line thereon. The spool (4) includes a front flange (4c), a rear flange (4b) and a bobbin trunk (4a). The rear flange (4b) is disposed rearwards of the front flange (4c). The bobbin trunk (4a) includes a plurality of coupling ribs (25) circumferentially disposed at predetermined intervals for coupling the front and rear flanges (4c and 4b). The bobbin trunk (4a) is integrally formed with the front and rear flanges (4c and 4b), while having a diameter less than diameters of the front and rear flanges (4c and 4b).
