The purpose of this paper is to summarize the changes of teaching and learning contents in the areas of "Number and Calculations" and "Number and Algebraic Expressions" in the Course of Studies for elementary and secondary school mathematics after 1945 in Japan. As a result, the followings are found out as three main characteristics. (a) There is a remarkable difference between the period of "Life-Unite Learning" (1945 — 1957) and the period of "Systematic Learning" (1958 — 1967) regarding to the teaching and learning contents and their sequences in these areas shown in the Course of Studies. (b) The contents and sequences shown in the Course of Study (1958) has been the prototype of those shown in the following Course of Studies (1968, 1977, and 1989). In the new one (1998), however, we notice that calculations are rather lightened; decimal numbers and fractions are introduced one year later than the before (1989); the using of algebraic expressions with alphabetic letters is shifted from elementary to lower secondary school mathematics. (c) The dealing with equations and inequalities in secondary schools is gradually lightened in recent years
