This paper treats a 3D graphics software development system called IntelligentBox. Especially it presents its aspects as an Internet-supported tutoring system. Using IntelligentBox, end-users can develop interactive 3D graphics applications by combining already existing 3D software components through direct manipulations on a computer screen. Since every software component of IntelligentBox is visible and manually operable, composite components are also visible and manually operable. A network communication facility is also provided as a certain software component. Using these software components, it is possible to rapidly develop a distributed 3D virtual environment where a tutor can teach a learner how to operate a target object of tutoring, which is represented as a 3D composite component, by real-time demonstrations via a network. This paper describes the availability of IntelligentBox as an Internet-supported tutoring system.