Service Oriented Architecture(SOA) is a flexible structure which does not affect other services even when a specific service is changed. It provides the platform with neutral interfaces independent of any others, where services are loosely coupled in a standard way. While ESB (Enterprise Service Bus) is a key technology for service-oriented architecture, few research and development for ESB has been done. In this paper, we designed and implemented the key components of ESB such as mediation service, message oriented middleware service, operation service, monitoring service, application connection service, and database connection service. The performance evaluation was done by measuring the message processing time for the number of messages with various sizes.