A light guide for an endoscope is equipped with an optical fiber. The optical fiber has an input side tapered portion and an output side tapered portion. The input side tapered portion is a predetermined portion of the optical fiber that includes an input end into which the illumination light enters the optical fiber, and the core of the optical fiber having a shape that becomes thicker toward the input end in the light input side tapered portion. The light output side tapered portion is a predetermined portion of the optical fiber that includes an output end through which the illumination light is output, and the core of the optical fiber having a shape that becomes thicker toward the output end in the light output side tapered portion. The core diameter at the input end is greater than the core diameter at the output end.
