We developed a conversation system which can participate in a group conversation. Group conversation is a form of conversation in which three or more participants talk to each other about a topic on an equal footing. Conventional conversation systems have been designed under the assumption that each system merely talked with only one person. Group conversation is different from these conventional systems in the following points. It is necessary for the system to understand the conversational situation such as who is speaking, to whom he is speaking, and also to whom the other participants pay attention. It is also necessary for the system itself to try to affect the situation appropriately. In this study, we realized the function of recognizing the conversational situation, by combining image processing and acoustic processing, and the function of working on the conversational situation utilizing facial and body actions of the robot. Thus, a robot that can join in the group conversation was realized.