Our community is facing serious problem: Aging Society. The population of elderly people is now increasing in Japan. Especially over 75 years old people is estimated to be up to 20 million in 2030. We have investigated in one of daycare centers which are facilities for elderly care. And we realized that communication is needed for its own sake in these facilities and active communication can cure even depression and dementia. Therefore we propose to cope with these problems using a robot as a communication activator in order to improve the effectiveness of group communication. We define group communication as one of the type of communication which is formed by several persons. This time, we focus on a recreation game named "Nandoku." Nandoku is a type of quize which can be described as group communication with a master of ceremony (MC). In this paper, we describe requirement for this system and system design. The system always selects its behavior and target (a participant in the game) to maximize "communication activeness." Communication activeness is defined as amount of several subjects'(ordinary three: A, B, C) participation, which are calculated with participants' face direction using camera information. For instance, if participant A is not fully participating by not making eye contact, the system is expected to select one of the behaviors such as "Can you answer, Mr. A?" to encourage A to participate in the game. We experimented with the system in a daycare center. Our results show subjects' participation is totally increased. That offers evidence that the robot can serve a practical role in improving the group communication as a communication activator.