This study speculated on the world of the Indian Ocean through terms of 西海(xihai), 西洋(xiyang) and 西域(xiyu). Originally, 西海(xihai) was a term with directionality based on Chinese world view, but it indicates the Mediterranean Sea, the Arabian Sea and the Red Sea as physical space along with cultivation of Silk Road on land. The Indian Ocean was recognized as 西海(xihai) or 西南海(xinanhai) in the Song and Yuan periods. the concept of 서양 has directionality starting from the coastal waters of Fujian and Guangdong, but the concepts of the east and the west that was examined from 『南海志』 published in 大德 years indicate the range central port cities had influence on and is spacial as it covers even religious and ethnic conflicts and cooperation. That is, 西洋(xiyang) indicates the Indian Ocean, but it also means a trade network in this area. The term of 西域(xiyu) is related to appearance of large historical stage. The Islam that began to grow through the Middle Ages was a center of wide historical stage over Europe and Asia under Mongol Empire. The Indian Ocean network was expanded inland and a key factor when it connected different civilizations was reciprocal trade. The Indian Ocean network connected local products each subcategory wanted to import. In particular, cotton which was produced in India was spread over each civilization through trade via the Indian Ocean network. 西域(xiyu) was a wide economic area where different civilizations were linked to guaranty reciprocal trade, not an east-west passage. The Indian Ocean network covered the Arabian Ocean along the western and southern coast of India and connected the Mediterranean Sea and the Red Sea on land via the Persian Gulf. It connected to the Arabian Ocean along the eastern sea of Africa, which formed a big link. Local products from East Asian products via large and small islands on the Indian Ocean, India, Java and Srivijaya empire were accumulated on this central link. It also connected Arabia, Asia Minor, the western and northern area of Africa, Iberia, India, West India and Yunnan civilizations. Port cities of each civilization were converged in a big link of the Indian Ocean while leading area of subcategories by connecting hinterlands. The term of 西洋(xiyang) was used when Chinese people explored such Indian trade networks and joined in them through the oceans. Important passages to the Indian Ocean were Guang-zhou and Ch'uan-zhou. They developed greatly as big cities that had China and East Asia as hinterlands.