This research investigates the Twitter network sphere of the 112th U.S. House of Representatives and the 18th Korean National Assembly members. Drawing from social network analysis, this study explores and compares structural characteristics of each legislative political network at diverse network levels – legislative, party and personal network. Mapping these networks highlights the major features of these two elite political networks grounded in a new social medium. Findings indicate that U.S. and Korean lawmakers have created and are enjoying affluent and multi-layered digital networks. Dynamic legislative-body networks, strong party networks, and a variety of personal networks with diverse partisan and bipartisan relationships demonstrate how politicians are agile at using new mediums. This research confirmed that these newly created legislative networks go beyond partisanship. Complicated structures demonstrate active and mutual interactions among lawmakers, and the political networks with large numbers of bipartisan tie relationships indicate that the political elite communicate, interact, and build relationships with each other rather than remaining disconnected or isolated. This research revealed new types of leaders – digital opinion leaders – emerging from newly created digital legislative networks: the most connected lawmakers; lawmakers who have great potential to coordinate party politics; the most sought after leaders; and most sociable lawmakers. By examining lawmakers’ patterns of relationship building in the network, this research tests whether these relationships are dependent on party position, ruling or opposition, in the network. In turn, this provides evidence for different uses of this new medium by party position in both legislative bodies. Detailed examination of Twitter use by political elites in Korea and the U.S. illuminate how this new media platform is being adopted by and changing politics in two distinct social and cultural settings. This new political arena, a fully digitalized and networked sphere where dynamic competition and cooperation occurs between political elites, has emerged as one of the political battlefields in politics today. / text