This paper analyzes the transformation of welfare policy in Japan in terms of the political crisis of a ruling party. First, welfare commitment in a period of Liberal Democratic Party`s(LDP) predominant party system would be an effective policy of a ruling party faced a political crisis, regardless of partisanship. Second, ruling party`s political instability, such as a decrease in turnout or support, raises opposition forces` political leverage, and then a ruling party reacts to a political crisis by providing policy compensation. Third, a minority or minimum size coalition government seeks to make a suprapartisan agreement and adopts path-dependent policy to reduce the loss of support. Fourth, if there are some institutional mechanisms to control a veto-power even in a coalition government, a prime minister can drive welfare-reform without political opposition. This paper shows a dynamics of Japanese welfare policy through analyzing the effects of a political crisis and an increase in liquidity on the direction of welfare policy in a historical context. Moreover, it provides some implications about how the ongoing issues of neo-liberalism and new welfare state lead to a policy-action.