In this paper, a remote operation system of a mobile robot on WWW browsers is constructed based on TCP/IP network techniques. Data of a CCD camera and sonar sensors on a mobile robot is transmitted to a client PC by CGI, Socket of Java API, etc. Real time performance is improved by such efficient transmissions. An user interface is developed to appeal visually to an operator using the drawing ability of Java applets. Additionally, a framework is proposed to display multiple robots on remote site to local WWW browsers.