This paper aims to explain the social and spatial change in a rural-urban fringe of the metropolitan area, focusing upon social networks for understanding the characteristics of socially mixed neighborhoods. The phenomenon is commonly known as konjuka, which is understood as “an established local community becoming more heterogeneous with the inflow of newcomers, ” and that situation causes various difficult problems in the local community. Previous konjuka studies have had some methodologic problems. For that reason, this paper introduces the social network approach in this geographic study.<br> A social network is a device for representing social structure which depicts persons as points and relations as connecting lines. One advantage of the social network approach is that the researcher is not confined a priori to the spatial units of analysis such as the neighborhood or the community. The other advantage is that the researcher can analyze the emergent property of networks.<br> In this analysis as a case study in Asahi-cho, Washimiya Town, Saitama Prefecture, the author draws on 1) fieldwork for describing the residential neighborhood relationships, and 2) a questionnaire survey to clarify the structure of personal networks.<br> The main findings are summarized in the following three points:<br>1) Established residents formed groups between neighborhood relationships throughout the community range but newcomers formed them only in the han range, which is one of the areal units of the local autonomy association. Residents tend to have cliques of intense social cohesiveness in their han range but such groups have little interaction among them.<br>2) Established residents had dense kinship and friendship networks in the proximity of their residential area. In the case of newcomers, however, women formed into a sparsely knit, spatially dispersed, ramifying structure. Men maintained personal networks in their workplaces and outer communities. In terms of intimate networks, women tended to have socially close friends who lived in near by neighborhoods or communities.<br>3) In the gender role in their households, women developed personal networks in their neighborhoods. Women whose children take part in kodomokai, i.e., the neighborhood group of elementary school pupils, play an especially important role in bridging the gap between newcomer groups and established resident groups.