The calibration results of the ocean color temperature scanner (OCTS) onboard the Japanese advanced Earth observing satellite (ADEOS) are presented in this paper. The goal of OCTS is to measure the geophysical quantities of the ocean (chlorophyll-a concentration, pigment concentration, etc.). They are calculated from the measured radiance by correcting molecular and aerosol scattering components, so the highly accurate calibration of the OCTS data is desired. For this purpose, OCTS is radiometrically calibrated using internal calibration sources (i.e., internal lamps, sun light, night times data, uniform target data), and external calibration source (NASA's airborne sensor underflights). It is also calibrated using the ground control points. As a result it was confirmed that OCTS data meets the specifications and provides accuracy for scientific use.