In the 1930s, Japanese rural society experienced a sudden shift from a period of overpopulation to one of outflow. Towards the end of the period, non-farm job opportunities as well as military mobilization increased, as a result, of which many young men in the farm sector left their families, including eldest sons who usually stayed at home as farm successors. The study investigates the reallocation of household labor force in response to the large-scale withdrawal of young males from agriculture. Quantitative analysis shows that agricultural work that was earlier carried on by the outgoing males was largely taken up by mothers and other adult women. The impact of the outflow’ , was a little stronger when the eldest son left the farm.