This paper examines issues related to the spread of COVID-19 infection and the establishment of restricted areas through the concepts of region and diffusion. From a spatial perspective, the spread of infection could be interpreted as the formation of homogeneous areas with a high proportion of infected people, consisting of (1) contact spread to neighboring municipalities, (2) nodal areas spread by daily activities such as commuting to work, school, and shopping, and (3) functional areas spread from the urban center to the central suburban city and its surroundings by stratified spread. As a result, uniform regions, which varied according to percentage of infected persons, were formed in concentric and radial patterns. On the other hand, in terms of the establishment of restricted areas, the declaration of a state of emergency attempted to limit the real areas with a high percentage of infected persons to the framework and scale of formal areas called prefectures, which caused various problems. In addition, the Priority Measures for the Prevention of the Spread of the Disease made it possible to set up a small-scale area of municipalities, but it can be pointed out that the living area (nodal area and functional area) created by people's daily activities must be taken into consideration.