A behavior control system and a behavior control method for a robot apparatus are disclosed. The behavior control system and the behavior control method for a robot apparatus include a function of adaptively switching between a behavior selection standard, taking into account the own state, required of an autonomous robot, and a behavior selection standard, taking into account the state of a counterpart, responsive to a situation. A behavior selection control system in a robot apparatus includes a situation-dependent behavior layer (SBL), capable of selecting a particular behavior from plural behaviors, and outputting the so selected behavior, and an AL calculating unit 120 for calculating the AL (activation level), indicating the priority of execution of the behaviors, for behavior selection. This AL calculating unit 120 includes a self AL calculating unit 122 and a counterpart AL calculating unit 124 for calculating the self AL and the counterpart AL, and an AL integrating unit 125 for summing the self AL and the counterpart AL with weighting by a parameter used for determining whether emphasis is to be placed on the self state or on the counterpart state, to output an ultimate AL. The counterpart is a subject of interaction of the robot apparatus. The self AL and the counterpart AL indicate the priority of execution of the behavior with the self and with the co8unbterpart as a reference, respectively.