This article investigates the effect of banks’ lending capacity on firms’ investment. To identify exogenous shocks to loan supply, we utilize the natural experiment provided by Japan's Great Hanshin‐Awaji earthquake in 1995. Using a unique data set that allows us to identify firms and banks in the earthquake‐affected areas, we find that the investment ratio of firms located outside the earthquake‐affected areas but having a main bank inside the areas was significantly smaller than that of firms located outside the areas and having a main bank outside the areas. Our findings suggest that loan supply shocks affect firm investment.