1. A behavior determining apparatus comprising: an elemental-behavior extracting unit configured to extract, from trajectory data in which positions of a traveling body in an observation area are held at predetermined time intervals, L (L is an integer equal to or larger than 1) elemental behavior quantities among a stopping time representing a total of time during which the traveling body is stopping, a stop frequency representing a number of times the traveling body stops, a walking time representing a total of time during which the traveling body is walking, a running time representing a total of time during which the traveling body is running, a direction change frequency representing a number of times the traveling body changes a traveling direction at an angle equal to or larger than a threshold angle, a sum of angle change quantities at the times when the traveling body changes a traveling direction, a sum of absolute values of angle change quantities at the times when the traveling body changes a traveling direction, a gravitational center set vector representing a set of gravitational centers of stop positions where the traveling body stops in respective divided areas obtained by dividing the observation area, and a pre-stop average speed obtained by averaging speeds immediately before the traveling body stops; and a behavior determining unit configured to determine a behavior of the traveling body from the L elemental behavior quantities.