This paper shows the architecture of IPS(Intermarket Payment System), an implementation of the electronic payment function for internet-shopping merchant system. Because the original purpose of commerce transaction is the exchange of money for goods or services, it is very important to prepare an exchangeable economic value or method. The electronic payment system is the hardware or software or both to process an electronic payment transaction. It has two type, the broker type and the electronic value type. The broker type means an intermediator between real bank network and internet commerce transaction. The electronic value type means a substitute for money in the real world. This paper shows the architecture and the function to implement the broker type electronic payment system. The system has two parts. One is the mediator part to support multiple payment systems and to offer common access methods for merchant system database. The other is the executor part to implement the payment protocol and to process payment transaction.