There is disclosed a user interface apparatus to which the user (player) can easily sensuoulsy become accustomed, and which can accurately recognize instructions (commands) that the user (player) intended. The user interface apparatus has a location/posture sensor (100) attached to the head of the user, and a location/posture sensor (200) attached to his or her hand, analyzes hand action on the basis of the relative position of the location/posture of the hand with respect to those of the head, and estimates the current action state from the analysis result. The apparatus then determines a user instruction (player command) on the basis of the action state.