An optical characteristic measuring apparatus includes a hemispheric portion having a reflective surface on its inner wall, and a plane portion arranged to close an opening of the hemispheric portion and having a reflective surface on an inner-wall side of the hemispheric portion. The plane portion includes a first window occupying a range including a substantial center of curvature of the hemispheric portion for attaching a light source to the first window. At least one of the hemispheric portion and the plane portion includes a plurality of second windows arranged in accordance with a predetermined rule for extracting light from inside the hemispheric portion.