A behavior estimating system is provided. According to the system, an estimated trajectory which provides the basis on which the behavior of an agent is controlled is generated according to a second model which represents a motion of an instructor in which the position and the displacing velocity of the position of a state variable and the time differential values thereof continuously change, in addition to the position of a characteristic point of a reference trajectory which represents a motion of the instructor and a plurality of first models which represent a plurality of shape characteristics of reference trajectories. A behavior manner corresponding to a first model whose fluctuation, which is allowed under a condition that an estimated trajectory passes a characteristic state variable or a range in the vicinity thereof, is the smallest and whose stability is the highest is estimated as the behavior manner of the instructor.