This paper is an empirical exposition of the relationship between bank deposit-loan interest margin and the interest risk, default risk, capital-asset ratio and various indicators which are believed to affect prices of bank products using banking statistics during the period 1992～1997. The empirical results show that Korean banks' interest rates have been deviating from the interest levels which should be fixed if the banks' business objective lies in the profitability. This proves that Korean banks management behavior is dictated by competitive size expansion rather than by profit maximization. Among many empirical findings, most important one is that the banks did not raise the interest margin in reaction to the higher credit risk, which implies the poor credit screening technique of banks. The paper concludes with suggestions for more rational strategy of determining profit-maximizing interest rates.