Using the case of female office workers as an illustrative example, this paper examines how the Japanese workplace has been constructed and reconstructed in gendered terms from the Meiji era to the present. The gendered nature of the Japanese workplace is often understood as distinctive when compared with that of other industrialized nations. While it tends to be viewed as the residue of « traditional discrimination against women », a closer look at history reveals the social-historical construction and changing nature of gendering in the workplace. « Men » and « women » were vague, ambivalent, and fragmented categories in the world of office work before WWII. By placing men in different occupations and ranks within the same category of male breadwinner, gender categories took shape in the postwar workplace, and by the end of the period of high economic growth the meanings of « men » and « women » became totally different from each other. The drastic restructuring of the Japanese workplace now under way, however, seems to be undermining the reality that has sustained the male breadwinning model, rendering gender categories, once again, more fluid.