A measure of interactivity not only can quantify the construct of virtual storytelling systems and thus make it possible to find the precise relationship between interactivity and other variables, but also can help ensure the effective development process of virtual storytelling systems. This study proposes a multidimensional scale model to measure the interactivity of conceptually and technologically diverse virtual storytelling systems. Using a survey research method, users' perceptions of interactivity of virtual storytelling systems were utilized for validating a scale model. This study suggests that multidimensionality should be incorporated into a scale model such as control, synchronicity, and communication. In particular, the findings of this study showed a possibility of sub-dimensions in the control dimension which is mechanical-oriented control and content-oriented control. The sub-dimensions can be explained as diverse features provided to the control dimension of interactivity.