This paper is an attempt to present a structural analysis of the religious system of the Sinhalese of Sri Lanka (Ceylon). Anthropological study of the religion and society in South Asia has made great progress since SRINIVAS'S classic "Religion and Society among the Coorgs of South India" first published (1952). SRINIVAS pointed out two major problems in his monograph. On the one hand, he introduces the concept of 'spread' in Hinduism (All-India, Peninsular, Regional and Local). He emphasized the relation between all-Indian and Local Hinduism, or the sanskritic and the non-sanskritic Hinduism. The idea of this separation has been developed by some investigators, e. g. REDIFIELD(Great Tradition/Little Tradition), MARRIOTT (Universalization/Parochialization), and MANDELBAUM (Transcendental/Pragmatic) , in the studies of peasent society. On the other hand, SRINIVAS demonstrates how the religious notions of good-sacred (pure) and bad-sacred (impure) determine Hindu caste hierarchy and caste behaviours. The 'pure-impure concept' (or 'pollution concept') correlating religion with social structure has been assumed to be the basis of the Indian caste system. Especially, HARPER demonstrates how there is a broad reflex of three-class-caste system (high-middle-low) in three grades (gods, deities, spirits) and of ritual status (pure, pure/impure, impure) . HARPER'S idea is a knot of SRINIVAS'S two problems. First, I examine the utility of the hypotheses of SRINIVAS and HARPER critically, and then outline the total religious system of the Sinhalese through the structural analysis of rituals. The doctorine of Theravada Buddhism and primitive religion has been fused in Sri Lanka since 3c B. C., but people's religious behaviour now is that of a single religious tradition that is Sinhalese Buddhism, which is closely linked with the great tradition (Theravada Buddhism) . Sihhalese Buddhism includes various levels of Supernatural beings. This 'Pantheon' is neither Theravada Buddhist nor a magical animist one, but a 'Sinhalese Buddhist Pantheon'. The 'Pantheon' is hierarchically structured as follows. (1) The Buddha : the repository of power and divine authority, (2) Gods (deviyas) : Guardian deities and local gods who have power and divine authority over a certain area, and subordinate to the Buddha as a super deity, (8) Demons (yakas) : demons, dead relatives, goblins, and ghosts who are completely malevolent, punitive, and causing fear in men's hearts. Besides these Supernatural beings, there are some mediators who mediate between men and the supernatural beings. (1) The Buddhist monks (bbikkhu) : Mediators between men and the Buddha who is an other worldly being, (2) The astrologers (sastra kariyas) : Mediators between this world and the other world. Buddhism is connected with other-worldly oriented things (lokottara), while Magical-animism (god worship and demon worship) is connected with things of this world (laukika). Both systems are not contradictory but complementary. So, Buddhist monks may visit an exorcist to obtain cures in the case of irrational illness. This self-contradiction can be solved by the clear distinction between lokottara and laukika. The binary opposition between Buddhism and Magical-animism may be seen in the opposition between Buddhism and god worship as well. The Buddhist temple (vihara) and the shrines for the gods (devale) are often housed under one roof or at the same site. There are regular rituals in the vihara (Buddha pujava) and the devale (devapujava).