This study establishes present value of total profit function for analyzing fixed rate mortgage and adjustable rate mortgage, and decides the optimal mortgage interest rate in order to get the expected present value of total profit. In this research, we find the factors for deciding mortgage revenue amount are interest rate and demand for mortgage. As for concerning profit for banks, the interest rate, demand, and quota for mortgage have positive effects for profit, and prepayment amount has negative effect for profit. Thus, while setting interest rate for mortgage, banks should concern benefit and cost with care in order to decide the optimal interest rate for mortgage.