It is important for conversational agents that manage multiparty conversations to recognize the group dynamics existing among the users. This paper proposes a method for estimating the conversational dominance of participants in group interactions. First, we conducted a Wizard-of-Oz experiment to collect conversational speech, and motion data. Then, we analyzed various paralinguistic speech and gaze behaviors to elucidate the factors that predict conversational dominance. Finally, by exploiting the speech and gaze data as estimation parameters, we created a regression model to estimate conversational dominance, and the multiple correlation coefficient of this model was 0.85.