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.
