To provide an optical fiber, a medical light guide, and a method for manufacturing the optical fiber that enable facilitation of manufacture and also an increase in utilization efficiency of light by improving a light scattering property.SOLUTION: An optical fiber according to one embodiment, being an optical fiber used for a medical light guide, comprises: a resin-made core 11d extending in an extension direction of an optical axis L； a resin-made cladding 11e covering the core 11d； and a plurality of grooves 15 that extend over one round around the optical fiber in a direction crossing the optical axis L and also are notched from a surface 11b of the cladding 11e to the core 11d. Each of the plurality of grooves 15 has such an almost triangular shape that, in a cross section including the optical axis L, a width at the surface 11b of the cladding 11e is wider and the width becomes narrower as the notch is deepened. A surface 15b of the grooves 15 is a rough surface that scatters light.SELECTED DRAWING: Figure 2【課題】製造を容易に行うことができると共に、光の散乱性を高めて光の利用効率を高めることができる光ファイバ、医療ライトガイド、及び光ファイバの製造方法を提供する。【解決手段】一実施形態に係る光ファイバは、医療ライトガイドに用いられる光ファイバであって、光軸Ｌが延びる方向に延在する樹脂製のコア１１ｄと、コア１１ｄを覆う樹脂製のクラッド１１ｅと、光軸Ｌに交差する方向に一周にわたって延びると共にクラッド１１ｅの表面１１ｂからコア１１ｄまで切り欠かれた複数の溝１５と、を備え、複数の溝１５のそれぞれは、光軸Ｌを含む断面においてクラッド１１ｅの表面１１ｂの幅が広く、深くなるにつれて幅が狭くなる略三角形状を有し、溝１５の面１５ｂは、光を散乱する粗面である。【選択図】図２
