要旨：This paper aims to theoretically and empirically investigate the relationship between agglomeration and urban industrial upgrading. If the high-tech industries relied on skilled labor, R&D, and specialized services more intensively, and the major channels of agglomeration economies were labor pooling, knowledge spillovers, and sharing the specialized local services, then urban agglomerations will gain comparative advantage and relatively specialize in the production of high-tech goods. Based on the urban industrial grade index developed in this paper, the association between agglomeration and urban industrial upgrading is confirmed by a panel regression using the data of Japan cities.