The transformation of the wrathful deity Mahākāla into the god of happiness and fortune Daikokuten in Japanese Buddhism. This study is devoted to the process of the transformation of the wrathful Hindu deity Mahākāla into the god of happiness and fortune Daikokuten in Japanese Buddhism. While in Hinduism and Vajrayāna Buddhism, Mahākāla was a wrathful deity, performing the functions of the Dharma protector, then as a result of the transference of this deity to the Japanese culture, his functions changed. The earliest examples of this process have been already marked in China, from where they later went to Japan. In the paper are traced the description of Mahākāla in the Japanese Buddhist textual tradition in the most notable Japanese text “Daikokutenjin-ho 大黒天神法” (“The Law of the Great Black God”), his iconography and the transformation in local folklore. The formation of Mahākāla iconography in Japan was influenced by a  process of the Shintō-Buddhist syncretism, which combined the esoteric doctrines of the Tendai school, traditional Japanese Shintō mythology, Buddhist cosmology and related elements of Hinduism. All these trends are also well traced in Japanese folklore. As a sequence, we could come to conclusion that the process of transformation of the wrathful Hindu deity Mahākāla into one of the Japanese gods of happiness Daikokuten was influenced by the desire to rid Mahākāla of his original destructive deadly attributes, since they were not combined with the original Japanese Shintō tradition, referring to death and its manifestations as an impurity.