A rotor of a spinning reel includes a rotor unit, and a fishing line guide portion. The rotor unit has a body portion that is rotatably mounted on the reel unit, and first and second rotor arms that each extend forward from opposing positions on the outer peripheral surface of the body portion. The fishing line guide portion is mounted only on the first rotor arm. The first and second rotor arms are formed such that a line L1 drawn along the pivot center axis of the fishing line guide portion of and a line L2 drawn through the width-wise center of the second rotor arm and substantially parallel to the first line L1 are on opposite sides of the rotational axis X of the body portion. A spinning reel rotor having a fishing line guide portion arranged on only one rotor arm can maintain rotational balance.