A waterproof rotor drive unit structure includes a driveshaft that rotates a rotor 11, a reel body 1, a housing member 4 and a lid member 6 that supports a pinion gear so as to be rotatable around a rotational axis of the driveshaft. A first annular projection 84 is disposed on an outer peripheral end of a rotor-facing surface of the lid member 6, the first projection 84 protruding toward the rotor 11 entirely around the rotational axis. The second annular projection 121, 122 is disposed on an inner peripheral wall 120 of the rotor 11 at a distance d3 from the first annular projection 84 in the radial direction, the second projection 121, 122 protruding toward the lid member 6 entirely around the rotational axis. The axial gap d1 between the distal end of the first annular projection 84 and the inner peripheral wall 120 is less than or equal to the axial direction dimensions H1, H2 of the second annular projection 121, 122.本發明提供了一種轉子驅動部防水構造,使水難以浸入到紡車式卷線器的收容單向離合器的收容部與轉子之間。該轉子驅動部防水構造具備:小齒輪3,其構成使固定於前端的轉子11旋轉的驅動軸;卷線器本體1、收容部件4以及蓋部件6,其將小齒輪3可繞著驅動軸的旋轉中心旋轉地支撐,具有將小齒輪3插入的開口,並收容小齒輪3的後端以及單向離合器5;環狀突起84,其設置在蓋部件6的轉子相對面的外周端部,並繞著旋轉中心以遍及全周的方式向轉子11側突出;環狀突起121以及環狀突起122,其與環狀突起84在半徑方向上隔開間隔,設置於轉子11的內周壁120,並繞著旋轉中心以遍及全周的方式向蓋部件6側突出,環狀突起84的前端與內周壁120的軸向的間隔為環狀突起121以及環狀突起122的軸向的高度以下。1‧‧‧卷線器本體2‧‧‧卷線筒軸3‧‧‧小齒輪4‧‧‧收容部件5‧‧‧單向離合器6‧‧‧蓋部件7‧‧‧轉子軸環8‧‧‧蓋板9‧‧‧密封部件11‧‧‧轉子17‧‧‧O形環21‧‧‧中心線32‧‧‧安裝部84、85‧‧‧環狀突起91‧‧‧螺釘111‧‧‧圓筒部112‧‧‧壁部113‧‧‧凸出部120‧‧‧內周壁121、122、123、124‧‧‧環狀突起
