This study analyzes how much credit ratings can explain the credit spreads implicit in bond yields. We find that there exists inconsistency of orders of credit spreads and credit ratings in about 8.6% of bonds. This finding implies that factors other than ratings may affect the credit spreads. We find that LEI (leading economic indicator), term spread of risk free rate, volatility of risk free rate, age of bond and EDF may affect the credit spreads. Credit ratings with these additional factors fully explain the credit spreads.