This study conducted an empirical analysis, based on the so-called Maturity Mismatch Hypothesis, of how unexpected changes in interest rates affect the common stock returns of Korean investment finance companies, and what relationship exists between the magnitude of this effect and the maturity differences of each company's nominal assets and nominal liabilities. The analysis results showed that the common stock returns of investment finance companies had an inverse relationship with unexpected interest rate changes; however, the sensitivity of this relationship was not found to have a statistically significant relationship with the maturity structure of assets and liabilities.