Amalgamations of cities in Japan have increased since the 1960s. Aiming at regional development in accordance with the progress of industrialization and urbanization, this process has created many new cities which have more than one “central” built-up area. These cities have had to face such problems as the areal distribution of public investment and the formation of new urban structures, yet before these problems can be considered, it is necessary to examine the changes in their urban structures. This paper does so for the city of Joetsu, which was amalgamated from the cities of Takada and Naoetsu, of similar size, in 1971. After amalgamation, the municipal government devised a plan to urbanize the built-up areas between Takada and Naoetsu. In the early 1970s, new administrative and cultural facilities were constructed in the Kida area close to Kasugayama Station, and since the 1980s many public facilities and large-scale retail stores have been built or located in the Sekikawa-Toubu area. Joetsu now has administrative and cultural centers in the Kida and Sekikawa-Toubu areas, as well as in the built-up areas of the former cities of Takada and Naoetsu. It can be said that the urban structure of Joetsu has become spatially dispersed because of the equal amalgamation of the two cities.