An illumination apparatus for an endoscope is provided at the distal end of the insertion section of the endoscope. The apparatus has a light guide which extends through the insertion section, has a light-issuing end located adjacent to the distal end opening of the insertion section. The light guide conducts light beams emitted from a light source device. An optical element made of a light-permeable material is arranged to face the light-issuing end of the light guide, and a lens is arranged in the distal end opening. The optical element has a light-receiving surface facing the light issuing end and a light issuing surface opposite to the lens. A depression is formed in the center of the light-issuing surface. Light beams emitted from the end of the light guide pass through the optical element and lens, and are distributed by the depression in the annular pattern whose central portions grow dark and whose peripheral portions are rendered bright.