Recently demands for marine development are increasing due to limitation of land-based resources, occurrence of the demands for the new materials and the increase of marine transportation among nations. Development activities in marine area give rise to external dis-economic effects to marine species and their habitats. Marine Spatial Planning(MSP) is a system devised to seek sustainable use of marine ecosystem, and to overcome conflicts between conservation and development This paper 1) analysed the effects of MSP in three aspects: economic, ecological and political effects, 2) explained reasons why MSP is necessary in the Korean marine policy and 3) suggested the prerequisites for successful adaptation of MSP in Korea.