本文主要研究日本央行實施緊縮性貨幣政策時，日本銀行業貸款組合變動與對實質經濟影響之關係，透過比較貨幣性衝擊、單純產出衰退及總和需求衰退對於銀行貸款組合的影響，以分析銀行在貨幣政策所發揮的功能。經VAR模型實證結果顯示，日本國內貨幣緊縮會使短期實質產出衰退、價格上升；銀行對於家計部門消費信用以及購屋貸款的放款減少、對企業的放款則增加。進一步檢驗不同規模企業貸款發現，銀行對大型企業的放款較為寬鬆，而對於中小企業的放款增幅較不明顯。另一方面，考慮信用標準擴散指數的VAR模型分析發現，日本國內的貨幣緊縮政策使銀行對於家計單位信用標準趨於嚴格的程度最大，再來依序為中型企業、小型企業及大型企業。這些實證結果支持銀行信用管道的存在，也說明銀行在貨幣傳遞機制中扮演重要的角色。 / The paper mainly studies the relationship between the change of Japanese bank loan portfolios and its substantial effect on economy during implementation of monetary tightening policy by Japan authority. Through comparison of monetary impacts, as well as the effects of the downturns in both output and real demand on bank loan portfolios, with the downturns are generated in a way that they produce the same dynamic real output and final demand path as that from a monetary downturn. The empirical results of VAR model reveal that the domestic monetary tightening in Japan would cause decrease in short-term real output and price level rise. General banks offer less consumption credits and house loans for households, but turn to increase loans for enterprises. When further examining the loans for enterprises of different scales, the paper finds that the banks take a looser attitude in offering loans to large-scale enterprises than to small and medium enterprises (SMEs), whose loans seem to have insignificant increase. On the other hand, after analysis of VAR model that considers the credit standard diffusion index, it is found that because of the domestic monetary tightening policy of Japan, the banks’ practices in their offer of credits appear to be strictest to households, and then less strict to SMEs and large enterprises. These facts prove the existence of credit channels of banks, and show the important roles that banks take in monetary transmission mechanism.