The aim of 'sociology of science' is to investigate the social and cultural factors having influence on the development of science, especially on natural science. This discipline was originated from R.K. Merton's work, "Science, Technology & Society in 17th century England" (1938). In this work, Merton made a research in the social-cultural environment of natural science stood at macroscopic point of view.<BR>After world war II, Merton's research was focused on the function of scientific communities, i.e. societies of scientists. In this context, the tacit assumptions brought in by him and his disciples are<BR>(1) the function of scientific communities is the most important factor having influence on the development of science, <BR>(2) the real scientific method is the organized empirical method, <BR>(3) scientists always migrate from one research area to another so that they can 'produce' articles much effectively and gain high reputation.<BR>In 1970's, new groups of sociology of scientists began to criticize these points. One of main trends is channeled by T. Kuhn's "paradigm thesis". This group made an assertion that science did not develop continuously, but that the mode of science changed discontinuously and in a Gestalt-like way. Sociologists of this group are investigating the inner structures of scientific communities from the empirical point of view. In this approach, one of the most useful techniques is regarded to be 'co-citation analysis' adopted by H.G. Small.