The cubic net radiometer is an instrument that is capable of measuring separately and simultaneously solar and long wave radiation fluxes for six directions with mutually perpendicular. Useful quantities necessary for study on complex thermal radiation fields such as radiation vector, mean radiant temperature, albedo and so on will be obtained using the cubic net radiometer. It consists of independent six pieces of the plate like environmental radiometer which is made of three kinds of heat flow meter with surfaces of different radiation properties. Several constants inherent in the environmental radiometer were calibrated compared with the measurement of the standard instrument except the corrective constant for air velocity. Indications of the cubic net radiometer showed good agreement with natural solar and atmospheric radiation fluxes.
