Virtual walkthrough system can be used for monitoring some areas, introducing view spots or learning history. Most virtual walkthrough systems use prepared images or 3D virtual objects to create the virtual environment and it is hard for the walkthrough system to be operated in real time. In some situations, real time walkthrough is important, and it is possible to construct a real time walkthrough system using an omni-directional camera which takes a 360-degree image at a time. In this study, we create an interactive walkthrough system with improved map projection panoramas from omni-directional images and evaluate the system. With improved map projection method, we acquire better-quality and more friendly panoramas than with original map projection method. The walkthrough system consists of an omni-directional camera, a server PC and client PCs. The server PC sends panoramas to clients, and the clients construct the virtual environments for walkthrough with panoramas and other prepared image and audio files. We evaluate this system by the effect of image projection methods, functions of walkthrough system and users’ answers to a questionnaire.