此篇論文研究當無通膨目標、存在固定通膨目標及央行宣示通膨目標之三種不同情況下，央行之最適貨幣政策。我們建立數個顯示不同通膨和產出比重之模型，並探討當央行偏離中位數投票者偏好時，對貨幣政策有何影響。 若社會福利函數中之產出的比重較重，在無通膨目標、存在固定通膨目標下，通膨偏誤皆較大。但央行宣示通膨目標時，無論通膨或產出比重較重，視其不同條件而定，通膨偏誤可能較大或較小。另外，央行偏離通膨目標的懲罰，罰責越重使央行宣告之通膨率對民眾預期通膨之影響可能越大，亦可能越小。 將央行偏離中位數投票者偏好之因素納入考量時，在無通膨目標、存在固定通膨目標下，社會福利函數中之通膨比重較重時，通膨偏誤仍較低，而央行宣示通膨目標時，通膨偏誤仍可能較大或較小。但引入央行偏離中位數投票者偏好時，在某些條件下，通膨偏誤可能進一步下降。 / The paper studies the central bank’s monetary policy under pure discretionary, noncontingent targeting and targeting with announcement. We construct models with different weight on inflation and output in the social welfare function. Furthermore, we introduce the central bank’s deviations from the preference of the medium voters into the models to show the effects on monetary policy. The inflation bias is larger when there is more weight on output in the social welfare function in the case of pure discretionary policy and noncontingent targeting. In the case of targeting with announcement, regardless of more weight on inflation or on output, the inflation bias is either larger or smaller under different conditions. Besides, a greater penalty on the central bank’s deviations from the inflation target may increase or decrease the effect of announcements on the public’s inflation expectations. With consideration of the central bank’s deviations from the preference of the medium voters, the inflation bias is still smaller when there’s more weight on inflation in the social welfare function in the case of pure discretionary policy and noncontingent targeting. In targeting with announcement, the inflation bias may still be larger or smaller. However, with the central bank’s deviations from the preference of the medium voters, the inflation bias can be reduced further under some conditions.