A light transmitter, which transmits light from a light source through a light guide comprising an optical fiber flux and which includes an optical system provided with a light refracting plane and a cylindrical reflecting plane which are interposed between the light source and a light incident end plane of the light guide. The distribution characteristic of light incident upon the light guide is improved by the actions of said refracting plane and said cylindrical reflecting plane so that a uniform light flux can be introduced into the light guide. As a result, it is possible to prevent uneven illumination as well as sunburn on the light incident end plane of the light guide by the light source.