We present a design and implementation of a Flexible Videoconference System, FVCS. FVCS aims to reduce the botheration of the users under operational environments with insufficient computational resources, such as the Internet environment with the small-scale computers at home and faces, by embedding flexibility to the conventional videoconference system. In this paper, we propose a design and implementation of FVCS with knowledge-based multi-agent framework. We implement some kinds of prototype systems of FVCS with different types of knowledge embedded in the agent. We also perform some experiments using the prototype systems to evaluate the adaptability of the systems in response to the observed operational situations. From the results of the experiments, the adaptability is influenced by knowledge of agent, and we conclude that the knowledge-based design and implementation is reasonable for construction of FVCS.