The process of developing Japanese electric warmer 'kotatsu ' was studied by way of examining the catalogues of three manufacturers of household electric appliances. As a result, the following points were clarified ; 1) The electric kotatsu was developed in 1957,and it spread over almost every family in Japan in the course of the technical and design development . 2) A high-grade electric kotatsu developed in 1975 , which looks like a piece of furniture rather than a sort of electric appliance, is an example of the development which has greatly changed the characteristics of an electric kotatsu. Now it plays a part of dining-table or table for a drawing room and a living room. Thus it has become very popular of all the Japanese families as a low table.