ABSTRAKWorld War II, the political system of Japan was characterized by the dominance of Liberal Democratic Party (LDP) in past several decades. Therefore, LDP, which has accumulated abundant of assets and developed a close and extensive relationship with business complex, has been won elections under competitive campaigns. This result aroused the accusation for unfair competition among political parties. However, the implementation of Political Parties Law (PPL) would like to influence the freedom of party politics, people's thought and assembly and association. This article tries to explore the purpose and motivation of making the Political Parties Law in Japan through perspective of comparative politics. Through analyzing the version of PPL proposed by political parties and interest groups, it reveals that the real motivation of Japanese parties is to standardize the management rules of parties and to promote the oligopoly of parties for maximizing the political power. On the other hand, interest groups are focusing on the convention and subsidies of parties. Consequently, the party politics of Japan will fall into the competition of oligarchy and bring politics as a serving role of business complex. That is, the expected effecet of PPL as a new institution is to continually promote the benefits of big parties, and interest groups tend to follow the path of market nules in their political development. Currently, the decline of Political Funds Control Acts has triggered the advocate of PPL as a good idea, but is also provides an opportunity for those actors to sponsor institutional arrangements which are favorable ther intereset, However, the implementation of PPLK will reduce the number of political parties, siden the gap between big and small parties, and raise subsidies for big parties because of the exclusion of small parties from participation.
