A simple two-country model of economic geography is constructed in order to examine the effect of tariff competition on the spatial distribution of manufacturing activities as well as on welfare. We show that when the transport cost is sufficiently small, tariff competition with firm migration leads to a core-periphery economy, where one of the two countries imposes no tariff in Nash equilibrium. We also show that when the transport cost is sufficiently large, tariff competition harms the welfare of the two countries, implying that each country is better off by mutually binding agreement of free trade.