We propose a communication activation robot and evaluate effectiveness of communication activation. As an example of application, we developed the system participating in a quiz-formed party game called NANDOKU quiz on a multi-modal conversation robot SCHEMA, and we conducted an experiment in a laboratory to evaluate its capability of activation in group communication. We evaluated interaction in NANDOKU quiz game with subjects as panelists using video analysis and SD(Semantic Differential) method with questionnaires. The result of SD method indicates that subjects feel more pleased and more noisy with participation of a robot. As the result of video analysis, the smiling duration ratio is greater with participation of a robot. These results imply evidence of robot's communication activation function in the party game.