The purpose of this paper is to clarify the concepts of "Seikatsu-Kagaku" under the world war II and home economics after the war. The concepts of "Seikatsu-Kagaku" and home economics are similar. "Seikatsu-Kagaku" was encouraged under the war, because it was considered to be useful for practicing the rational life. However, home economics was trivialized after the war. The concept of "Seikatsu-Kagaku" was dealt with by several scholars. This paper takes up three scholars who dealt with "Seikatsu-Kagaku". On considering the tendency of home economics in post war Japan, home economics of elementary and secondary education are especially focused on, because they had some problems more conspicuous than that of higher education. Although it was out of step with the aims of its establishment, home economics of secondary education became the required subject for only girls. This research conciders the reason why home economics in post war Japan was trivialized.