1) Characteristics of Child Mentality and Religion: From the view-point of the contemporary developmental psychology, it is reasonable to regard the religious mentality in children as a product of their development. One of the best achievements which show the reltionship between religion and the characteristic of child mentality was made by J. Piaget. He thought that the characteristics of child mentality could be explained by the word “Egocentricism,” and that the world conception of children could be said “Animism,” “Realism” and “Artificialism.” This idea of his gives an influential suggestion on the origin of religion. In the child mentality, there exist religious elements as such. 2) Magic and Divination in the World of Children: Children live in the world of fairy tales, in which there are many magical elements. Children enjoy these since they do not possess the causality as grown-up people. They accept the magics divinations which are fitted to their community, while they create their own magics and divinations. 3) Religious Sentiments: What makes a behaviour religious is “la notion de sacre” as E. Durkheim said, or “Das Heilige” using the words of R. Otto. This is almost equal to the meaning of English “awe,” which, however, means strictly the complex of various emotions: that is Wonder, Selfsubjection and Fear, according to W. McDougall's papers. Therefore, until such emotions appear in child mentality, the true religious feeling does not come out. 4) Child Mental Attitude to the Established Religions Though many studies were done on this subject, here is a graduation thesis “The Development of Religious Consciousness in School Children” by M. Horie of Kobe University, who questioned about such established religious conceptions as God, Spirit, Haven and Hell and so on. And the children between young childhood and school-childhood have general tendency of accepting easily what they are told because they are too ready to imitate and believe. 5) The Process of Acquiring Religious Ideas in Children: As to the subject, J. B. Pratt thinks that (1) the indirect influence of the actions of older persons.(2) direct teaching on religious subjects.(3) the natural development of the child's mind are the working factors. Children acquire the religious ideas as they are taught, due to their imitative and repetitions qualities and suggestibility. But from about the end of school-childhood to the puberty their interests in the external side of religion become less. But in the latter period of adolescence when they contemplate the problems of life, they begin to turn their thoughts to religion, and “Conversion” often comes about at this step of life.