This research investigated to what extent social media use and motivation contributed to the bridging/bonding social capital and social, political participation by using the national survey on high school and university students. In particular, this research divided social media into two groups: open and closed one. The result of analysis showed that the use of open social media reinforced bridging social capital and that of closed social media did bonding social capital. Motives for social media use affected both bridging social capital and bonding social capital. Social media use and motive all had a positive influence on social, political participation. In conclusion, the effect of social media on social capital may be decided by the characteristics of social media and the purpose of social media use.