Since the end of World War II, the Japanese economy has experienced two types of ‘dual structure’ issues among occupational groups. The period before the war until 1950 consisted of large-scale companies stemming from zaibatsu (financial cliques) and indigenous domestic industries. The health disparities across occupational groups, often observed in the West, increased between the pre-war period and the 1950s but declined in the subsequent high economic growth period. The decline in health disparities was aided by economic democratization policies, active labour union functions, and post-war economic growth. Near-total employment was achieved, at least among male workers, in the late 1960s to early 1970s. Later, recession in the wake of the bursting bubble economy after 1991, and the subsequent economy-first policy, brought another dual structure: regular employees versus lower-paid ‘precarious’ employees. The latter group includes many women. Stressful working conditions including long working hours among specific occupational groups may cause unique patterns of health disparity among Japanese workers.