The purposes of this research were to examine the degree of loneliness and the structure of social network in the aged. Subjects were 416 aged above 65 years old who lived alone. The results showed that the score of loneliness was unexpectedly lower and there was no sex difference. The loneliness was associated with the number of supporters and the amount of interaction in interpersonal relationship. The degree of loneliness was lower when subjects had many supporters and many contacts. It was found that positive social interaction function was most important for decreasing loneliness.