This study asks how social movements have been worked on party politics in South Korea, one of newly democratized countries in the Third Wave of Democratization. Today, South Korea is Known as one of the countries with active social movements. Meanwhile, because of historical legacy of authoritarian rule, regional antagonism, and factionalism, party politics in South Korea has been unstable compared with other democracies. Though the state has attempted to grow 'healthy political party culture by laws and administrative guidance, the efforts havenot contributed to stable party politics. As a result, political parties in South Korea have had insuggicient capacities to connect the state and the civil society. Instead of the unstable organizations of political parties, loosely organized social movements have made the efforts to connect the state and the civil society. More exactly, social movements have pressured political parties mobilizing street actions, mass media, and social networking services. In the case of the impeachment of President Park Geun-hye in 2016, for example, social movements oromoted opposition party lawmakers to prosecute the President. The result of the analysis in this study indicates that social movements can play the role to cover the malfunction of political parties. Though traditional models of party politics see parties as actors to connect the state and the society, South Korea's ones havenot worked as the connecting actors. Instead, social movements have connected the parties and the society. This is one the reasons why South Korea has sustained democratic party politics in spite of the malfunction of individual parties. Extendedly, the result of this study can be applied to other democracies where de-organization of politics and society proceeds.