A spinning reel rotor includes a cylindrical portion, first and second rotor arms, a bail arm, and a second cover member. The cylindrical portion is mounted rotatably to one end of a reel unit. The first and a second rotor arms extend in a direction away from the reel unit while being curved outward in radial direction from a position in opposition, with respect to the radial direction, to an end of the cylindrical portion on the reel unit side. An aperture is formed in the second rotor arm. The second cover member covers the outside of the second rotor arm and has through holes for adjusting its mass. The through holes expose a portion of the aperture. In this rotor that has a rotor arm provided with an aperture, variations in the rotational balance of cover members due to different degrees of exposure of the aperture are suppressed.