I estimate a bivariate output-price structural vector autoregression (VAR) model for Japan to decompose inflation rate time-series into two components explained by aggregate demand (AD) and aggregate supply (AS) shocks. For the modelfs identifying restriction, I assume that the long- run elasticity of output with respect to permanent changes in price due to AD shocks is zero; i.e., an AD shock has no long-run impact on the level of output. Dynamic properties of the estimated model are shown to be generally consistent with the predictions of the conventional AS-AD framework. The main features of the historical decomposition are the following: (1) the inflation rate explained by the AD shock shows a procyclical swing since 1970; (2) the inflation rate explained by the AS shock temporarily spikes during the two oil crises and experiences a large countercyclical swing in the 1990s; and (3) the coincidence of large and negative AS and AD shocks explains the combination of price stability and output stagnation during two recessions in the 1990s. These results are qualitatively robust to the sectoral shocks, alternative choices for the price variable, and assumptions for the lag length of VAR and the long-run elasticity of output with respect to permanent changes in price due to AD shocks. However, the bivariate approach does not allow the identification of more than three types of shocks with different dynaic effects on output and price. It might be necessary to expand the model to deal with this limitation.