Mazu was a Chinese sea goddess worshiped by fishermen, villagers, maritime merchants, and local officials in the Sinic world including Japan, Korea, Vietnam, and the Ryukyu. Kingdom. In a sense, the Chinese cultural sphere was also the "sphere of Mazu belief." Compared with China's other neighboring nations, Japan settled at a deeper level of localization, turning Mazu into a Shinto deity, worshiping the Chinese goddess in the Shinto way, and enshrining her along with other Shinto deities. In the Tokugawa period, Mazu was worshiped by the Japanese as the manifestation of different Shinto deities. Based on Japanese primary sources, this study investigates the Shintoization of Mazu in Tokugawa Japan using Funadama belief among seafarers and shipbuilders, Noma Gongen belief in the Satsuma domain, and Ototachibanahime belief in the Mito domain as the main points of reference. Mazu was associated with Funadama, the Japanese protector god of seafarers, in different parts of Japan. In the Satsuma and Mito domains, Mazu belief differed tremendously from that in China in terms of religious titles, festival dates, forms of worship, and functions. This research aims to deepen our understanding of how Chinese folk religions were incorporated into the Shinto framework of Tokugawa Japan and the nature of the popularization of Chinese culture in Japan through the lens of localization.