Portfolio optimization using loan is formulated as a chance constrained problem in which the borrowing money from loan can be invested in risk assets. The chance constrained problem is proven to a convex optimization problem. The low interest rate of loan benefits borrowers. On the other hand, the high interest rate of loan doesn’t benefits lenders because such a loan is not often used. For deciding a proper interest rate of loan that benefits both borrowers and lenders, a new method is proposed. Experimental results show that the loan is used completely to improve the efficient frontier if the interest rate is decided by the proposed method.