This study tries to inquire into the function of social networks among married men and women in rapidly urbanizing Korean society. Social networks here include those of kins, friends, neighbors, voluntary association members, and office colleagues. The function of social networks refers to the affective, household affairs aid, material, and sociable functions. Followings are the important results of this study. Firstly, the functions of kin networks are the most important among the five networks, which verifies the fact that kins are still considered the primary source for functions of social networks. Friendship networks are relied on when one needs psychological help and sociability. Neighbors are found to perform the highest degree of function when one needs daily miscellaneous helps. It turns out that funtions of voluntary associations are the lesat important, which is different from the situation in western societies. The function of sociability is more or less high in networks of office colleagues, which is probably due to the fact that one tends to spend most of his daily life with office colleagues, sharing many social activities with them. Secondly, Networks of kins, friends, and neighbors perform the highest degree of functions for those in their thirties and fourties. But those of voluntary association members and office colleagues perform a higher degree of functions, as one`s age and family life cycle are higher. The function of sociability gets more important as one`s age gets higher in all the networks. This means that one extends his social networks to the secondary one, keeping varying kinds of social activities, as one gets older. The degree of functions of kin and friendship networks is the highest, when one`s socio-economic status belongs to the middle group. And that of voluntary association members and of office colleague networks is the highest, when one`s socio-economic status belongs to high group. Whereas that of neighborhood network is the highest when one`s socio-economic status is lower.