This paper constructs a theoretical model of political business cycles in a Parliamentary system and tests predictions and hypotheses of a theoretical model against the post-war Japanese data. Unlike in a presidential system, the timing of a general election is an endogenous policy variable in a parliamentary system. Thus, one of the interesting questions in a parliamentary system is whether elections cause business cycles or economic expansions trigger general elections. Empirical analyses of the post-war Japanese experience strongly indicate that the Japanese government did not manipulate policies in anticipation of approaching elections as political business cycle theories in a presidential system indicate. Instead, general elections were usually held during times of autonomous economic expansion. In other words, the Japanese government opportunistically manipulated the timing of elections rather than the economy.