This paper presents the results of the significant application of LANDSAT data to the monitoring of marine environment around Japan. In previous papers presented to an I.A.F. Congress, the author described the results of digital analysis of water pollutions such as industrial effluent, river effluent and red tide which is caused by the abandoned growth of plankton influenced by the nutritious water, using LANDSAT-1 and LANDSAT-2 MSS data compared with airborne remote sensing data and sea truth data obtained by ship and stationary buoy. In this paper, the author tried the analysis of MSS and RBV data obtained by LANDSAT-2 and LANDSAT-3. About the digital analysis of MSS data, the author tried color slicing analysis and similarity analysis using IMAGE-100 and FACOM PIA system. The main topic of this paper is the monitoring of river effluent from rivers such as the Kumano River, the Yoshino River and the Ishikari River. The Kumano River is noted as its polluted water with suspended substances caused by the effect of storage dams for hydraulic power stations located along the upper part of the river. The Yoshino River, which flows into Kii Channel, is the biggest river which flows into Seto Inland Sea area stipulated by “Special Rule for Observation of the Environment of Seto Inland Sea”; it is well known for its nutritious water and it reduces the water quality of Kii Channel, Osaka Bay and southern part of Harimanada. The Ishikari River, which flows into Ishikari Bay, is also noted as the biggest river in Hokkaido, northern part of Japan, and its polluted water with turbid water caused by beat and coal mine located in the upper part of the river. For the purpose of the monitoring of river effluent, the author tried both analog and digital processing analysis and good results were obtained. The second topic of this paper is the classification of water mass around Seto Inland Sea. In Osaka Bay, Harimanada and Kii Channel, a portion of Seto Inland Sea, the author tried digital analysis of LANDSAT MSS data including high gain mode data, which is received and reporduced by Earth Observation Station of National Space Development Agency. This station is constructed in Hatoyama Village near Tokyo, and it started its operation in last January. The third topic of this investigation is detection of oceanographical phenomen such as tidal front and internal wave. Along the coast line of Kumanonada and southern Hokkaido, we could recognize the existence of coastal current in RBV imagery and, as the results of this investigation, the tidal front in junction point of water mass and internal wave are also inquired. Through this investigation, the author tried comparison with the result obtained by airborne remote sensing and sea truth data too.