In a spinning reel for fishing, a fishline guide roller is rotatably supported on a bail support arm pivotably mounted on a rotor. The guide roller has a flattened shape such that a ratio of an axial length of the roller relative to a diameter thereof falls within 0.10-0.40. Further, the guide roller is formed with a narrow fishline guide groove so that a ratio of an axial length of the fishline guide groove relative to an axial length of the roller falls within 0.05-0.35. It is possible to make a fishline guide roller small in weight and size and to restrict axial motion of a fishline along the guide roller which, among other advantages, reduces line twist in the fishline.