A waterproof rotor drive unit structure includes a driveshaft that rotates a rotor, a reel body, a housing member, and a lid member that supports a pinion gear so as to he rotatable around a rotational axis of the driveshaft. A first annular projection is disposed on an outer peripheral end of a rotor-facing surface of the lid member, the first projection protruding toward the rotor entirely around the rotational axis. Second and third annular projections are disposed on an inner peripheral wall of the rotor at a distance from the first annular projection in the radial direction, the second and third projections protruding toward the lid member entirely around the rotational axis. The axial gap between the distal end of the first annular projection and the inner peripheral wall is less than or equal to the axial direction dimensions of the second and third annular projections.
