The Four Heavenly Kings have been represented from early Buddhist art in India until today in East Asia. There are two types of distinctive iconography of the deities: a king-like appearance in India and Southeast Asia and a warrior-like appearance in Central Asia and East Asia. Exactly when, where, and why this epochal change occurred is the subject of this thesis. The role of deities seen through images in Korea has been interpreted only in terms of the literal meaning of their Sanskrit name, Lokapala, `protectors of the world.' This dissertation tries to resolve matters of cult and iconography of the deities focusing on causal factors rather than resultant appearance, by considering what kind of indigenous thoughts were involved in creating Lokapala's iconography in India in the first place; what principally caused the change of iconography in East Asia; and what kind of religious intention was at the background of commissioned imagery in Korea. In the dissertation the change of iconography is viewed through the development of Buddhist doctrine, Hinayana and Mahayana; the role of Lokapala manifested as imagery in Korea is interpreted from the standpoint of the practitioner associated with the Buddha's relic cult. Indian indigenous thoughts are involved in the basic iconography of the deities, and regional differences in iconography were caused by differences in the cult of the deities as based on differences between Hinayana and Mahayana traditions. Armor, which is the distinctive element that does not appear in Indian images of the Lokapala, symbolizes the Mahayana path, emphasizing the Bodhisattva's intention to help living beings attain Buddhahood. The inner function of imagery of the deities in Korea, almost all of whom are represented on sarira reliquaries and stupas, is to affirm the living presence of the Buddha manifested as sarira preaching the Law in a space symbolized as a stupa.