This paper shows actual use of Social Media and its motives of information-sharing. Now there are over 50 millions social media users in Japan, and they share their feelings, opinions, tips and other things every day. What make them to write and upload so much information? The desire of friendship, expression, or recognition? In this paper, we focused especially reciprocity and tried to show the relationship between information-sharing and reciprocitical motive. Our analysis are based on the internet survey whose research object are Facebook or Twitter users.
