A method for directly measuring water-leaving radiance using an above-water sensor with a domed cover painted flat black has been proposed. In order to confirm the validity of the result of this method, field experiments have been conducted in Katagami Bay. Radiances measured by this method are slightly less than those obtained from the vertical profile of the upwelling radiance in the sea. This can be attributed to self-shading due to the shape of the instrument used in this study. The advantages of the proposed method are that it does not require empirical processes and minimizes manual procedures after measurements.