This article examines locality of the beginning and middle period of plain coarse pottery culture by comparing distribution and locational characteristics of plain coarse pottery relics centered around the mid-western area of Korea. In addition, the gradual transition to the middle period of the rectangular dwelling sites, which show the traits of the beginning period plain coarse pottery culture, will be discussed. According to geography and each relic`s features, the area under investigation are divided into four relic groups Han river` valley, Ansong river · middle and upper Keum river valley, western coastal area adjacent to middle - lower Kum river valley, southern area of Mankyoung river valley relic groups. The investigation results of each relic group reveal that the selective acceptance and changes of the middle period of plain coarse pottery culture occurred while characteristics of the beginning period prevail in northern areas of the middle upper Keum river valley. In particular, Songkung-ni type round dwelling sites have never been found in Han river valley. In Chon-nam Province, the adaptation of Songkung-ru type round dwelling structure partly took place, slim rectangular or rectangular dwelling sites underwent squarization and the traits of the beginning period culture such as pots with holes coexisted. This, therefore, exemplifies that the traps formation from the beginning period of plain coarse pottery culture into the middle period, was the most active in Ansong river middle upper Keum river valley areas which formed the northern boundary of Songkung-ni type round dwelling culture can be witnessed in the southern areas of middle-lower Keum river valley through dwelling pattern and accompanying artifacts whose traits of the slim rectangular and rectangular dweving pattern are almost absent from, In this study of the locality of the plain coarse pottery culture I hope to establish a basis for better understanding of the continuity between the beginning and middle period of plain coarse pottery culture and cultural properties of Songkung-ni type round dwelling sites of the middle period which is considered a turning point of the plain coarse pottery culture in Korean history.