Abstract
This paper summarizes the results of a study on how mobile phones are used among high school students in Japan, and have what are their impacts on human relations. It is estimated that the use of mobile phones exerts a great influence of interpersonal relationship among high school students. The younger they becomes, the more friends they have. However, the frequency of their communications does not increase. It is presumed as follows that they are increasing the tendency to consider one to be an intimate friend by registering one's name in the memory of their mobile phones.