An illumination apparatus for an endoscope guiding externally-entering light to a transparent light-guiding body including an annular-shaped annular portion, the annular portion including inner and outer circumferential faces, and making the light exit from the annular portion as illuminating light, wherein the light-guiding body includes: a notch portion formed by cutting out a part of the annular portion so as to form a line extending perpendicularly from the outer circumferential face toward the inner circumference side of the annular portion from a line extending from a point on an outer circumference of a circle in a cross section of the annular portion; and an incident portion that allows the light to enter in a direction along the line extending from the point on the outer circumference, the direction being a direction perpendicular to a cutout surface of the notch portion provided in the annular portion.