In this study we made clear the spatial composition of "Zaigo-machi" in the Tonami Plain by a case study on "Tuzawa." This small town is a typical Zaigo- machi established to accumulate property tax from neighbouring villages in 17th century. We analyzed the town in terms of compositions of the premises, roads and watercourse networks and townscape. We came to understand that the town was divided into two districts, and that the planning of watercourse and road had been a regulating factor bringing those two districts consistency in their townscapes.