In Nagano prefecture in 1970s, high school teachers of home economics education developed coeducational curriculum in home economics education, despite the government's provision of the home economics only for girls. This explores the reasons why the teachers worked toward the coeducation of home economics and situations that enabled them to do so. The former teachers who had practiced coeducational home economics were interviewed, and their life histories were collectively analyzed from the viewpoint of "personal time," "social time" and "historical time." Results are as follows. 1. The teachers' critical thinking was cultivated in the circumstances of their families, schools, communities and society during and after the World War II. They became aware of gender discriminations, and hoped to realize gender equity in education and society. 2. The teachers questioned the contents of textbooks of home economics that differed from the actual conditions of student's daily lives. These questions and desires for gender equity encouraged them to struggle for the coeducational home economics. 3. The teachers met at the research meetings of the Educational Culture Congress. By learning the philosophy and contents, they independently created the coeducational curriculum of home economics, and wrote the text book. The Teacher's Union in Nagano prefecture supported their activities.