Recent psychological studies on human moral development can be summarized as psychoanalysis approach, behaviorism approach and cognitive approach. The leading theorist of cognitive approach such as Kohlberg asserts that morality is development by moral judgment and moralistic conception. Assuming that the basis of cognitive moral development is cognitive growth, Kohlberg has developed Piaget's moral development theory which gave a considerable effect on cognitive growth theory. The theory that moral judgment is based on cognitive development is formed by Piaget. Piaget's theory that moral judgment is reflected in the cognitive growth is adopted by Kohlberg, whose theory is that moral growth is continued by degress in the same way that children's cognitive power is developed, and the development of moral judgment is made by levels in a sequence regardless of cultural, racial and national differences. Therefore Kohlberg divides the levels into three; 1) preconventional morality 2) conventional morality 3) post-conventional morality and this three levels are again divided into six . 1) obedience and punishment orientation 2) naively instrumental orientation 3) good-boy orientation 4) authority and socio-order maintaining orientation 5) contractural legalistic maintaining orientation 6) conscience or principle maintaining orientation According to Kohlberg, children's moral judgment is developed by three levels; from the first through the second to the third one, and the sequence is not in disorder. The process is continued according to the role taking power and cognitive equilibrium which is the extensive conception of equilibration model of Piaget's cognitive development theory. However, although the level of moral judgment requires a certain level of cognitive development, high level of cognitive development does not necessarily result in high level of moral judgment. When we consider that moral judgment and cognitive development are different elements, it is a controversial matter whether they have necessarr relations or not. This problem requires succeeding studies, revision and supplement. As a conclusion, theories of Piaget and Kohlberg provide many problems to be considered for school education.