Service broker is a software component that maps user's request to proper services. By using the broker, users can access various services without any knowledge of the services. However, design of the service broker for GCE (Global Computing Environment) is quite difficult because a broker cannot cope with all the information of services which are spread over the world. Thus, we need to build new architectural foundations for global service brokering. In this paper, we propose a scalable broker system for GCE based on the federation of personalized brokers. In our broker system, every user can have a service broker. The broker maintains the information of services related to the user and exchanges the information with neighboring brokers if necessary. As a result, the broker can provide proper services to users faster and a burden of brokers can also be decreased. Experimental results show that the proposed service broker can reduce the average service discovery time and the average operation overhead of each broker comparing to other brokering architectures.