本文探討銀行多角化對利潤及風險的影響進行實證分析，以分散收入來源及放款組合來定義銀行多角化，探討在銀行規模及經濟成長變動不同的情況下，多角化經營對銀行利潤及風險的影響為何？本文研究期間為1997到2009年，研究對象為台灣本國一般銀行與中小企業銀行，合計41家，共計462筆觀察值進行實證分析。本文結果顯示本國銀行多角化經營策略對於績效的影響不一，非利息收入比率與淨利息邊際呈現負向關係，且分散放款組合可顯著降低逾放比率，符合投資組合理論，然而，放款多角化對於非金控旗下的銀行或小規模銀行的風險調整後資產報酬率有顯著負向影響。當銀行規模越大，對利潤而言，分散收入可增加股東權益報酬率，但對風險調整後之股東權益報酬率影響不顯著。對風險而言，分散放款組合與收入來源可降低逾放比率。當規模越大，收入來源多角化經營，可達範疇經濟之效益。當經濟成長衰退，分散收入或放款均可提高風險調整後之資產報酬率與降低逾放比率。當經濟成長減緩，則比較能夠看出多角化分散風險的好處，減少經濟成長下滑對銀行造成的衝擊，但於金融危機時期，多角化經營未必有利。

This study constructs the dimensions of bank diversification in terms of loan portfolios and income sources. First of all, we examine the impacts of bank diversification on bank profitability and risk. Furthermore, we investigate the impact of bank diversification on profitability and risk based on the bank size and the economic growth. This paper focuses on 41 Taiwan domestic banks from 1997 to 2009. This study employs 462 observations to conduct the empirical analysis. The results show that noninterest income ratio is negatively related to net interest margin. Furthermore, loan portfolio diversification can effectively reduce the nonperforming loan ratio. These results are consistent with the traditional portfolio theory. However, to non-FHC banks and smaller banks, diversification in loan portfolios has significantly negative effect on risk adjusted return on assets. In terms of the bank profitability to the income diversification, large banks earn higher return on equities. However, the bank size has no significant effect on risk adjusted return on equities. Diversifciation in loan portfolio or income sources reduces the level of non-performing loans. Therefore, diversified banks can create the benefit of scope economics when the bank size becomes larger. Bank profitability, risk adjusted returns, and the nonperforming loan ratio benefit under slumping economic growth because of the diversification on loans and revenues. Therefore, the benefits of bank diversification are easily observed when economic growth slows. Diversified banks are able to maintain or even improve their profitability during the economic downturn. However, it might not be the situation during the financial crisis.