The Internet has become one of the most important tools. A huge amount of data is communicated in the Internet all over the world. The management of data traffic is very important under such a situation, because the computer transmits lots of unnecessary data though it is infected by a computer virus and the network is not well managed. A monitor of data traffic, therefore, should be required for recognizing such a situation. This paper describes the monitoring and control system of communication data. The system consists of an agent and a manager. The agent monitors the communication data in his own computer and reports the result to the manager. On the other hand, the manager receives and visualizes it to find abnormal data traffics with several kinds of graphs. The system also has the functionality to restrict the specified data transmission. The proposed system makes it possible that an event and a bottleneck of network system can be found and solved easily.