1. A traffic line creation device for creating a traffic line representing a motion trace of a tracking target, the device comprising: an object detection unit which detects the tracking target from an image frame to create detection result information including a detected area of the tracking target; a state determination unit which determines a state of the tracking target based on the detection result information and detection result information at the time when the state of the tracking target was a normal state; a reference point creation unit which creates a reference point of the tracking target by using the detected area with a process corresponding to the state determined at the state determination unit; and a traffic line creation unit which creates a traffic line representing the motion trace of the tracking target by connecting a plurality of the reference points created for a plurality of the image frames.