要旨：This paper investigates whether agglomeration discourages households’ fertility decision making. A theoretical prediction shows that higher costs of education and housing for rearing children in denser areas have negative effects on fertility. In an empirical analysis, we exploit social survey data to control for households’ unobservable characteristics. Furthermore, we control for costs of migration, which also discourages fertility. We offer robust evidence that agglomeration measured by population density discourages fertility. We also find that rural-urban migrants have fewer children than stayers in rural and urban areas, suggesting that households who move to urban areas are strongly affected by costs arising from not only agglomeration but also migration. On the other hand, there is no significant difference in the number of children between urban-rural migrants and stayers in urban and rural areas.