Drastic changes in the demographic structure of Japan, that is, the decline in the fertility rate and the growth in the aged population, and their possible consequences have been seriously discussed by scholars, policy makers, and the media. The continuous decline of the fertility rate raised people's concern over the reduction in the productive labor force and the potential imbalance in the future between contributions and benefits of social security. The ratio of young workers to the retired population has been declining rapidly, and the support of the elderly is becoming the burden of the working-age population. Japan has been characterized by the least favorable work setting for women, as exemplified by the discontinuous pattern of work among mothers, the large extent of wage gap between men and women, and the very low proportion of women holding managerial positions. In this paper, I would like to explore the affect of mothers' decision to work and the extent of their contribution to the household economy. This paper is divided into the three parts. First, I will show the trend in the fertility rate and the female labor force participation rate in Japan since 1960, and provide an overview of recent studies on married women's labor force participation. Second, I will examine mothers' working pattern, especially focusing on the continuation of work before and after the first childbirth in Japan. Third, I will compare mother's work in Japan with that in other industrial nations, focusing on the extent of their contribution to the household economy.