Tracking assistance to reduce a burden on a monitoring person, includes search condition setter setting a search condition by user operation, tracking target setter setting, as a tracking target, a person designated by monitoring person's operation to select a tracking mark on a tracking target search screen displaying a video conforming to the search condition, confirmation video presentor displaying tracking target confirmation screen displaying video of a person having a highest possibility of being the tracking target from each camera as a confirmation video, video display period setter that in a case where the tracking mark is not displayed in the tracking target on the tracking target search screen, sets a video display period by the user's operation, and in-camera tracking information corrector correcting the tracking information to display the confirmation video on the tracking target confirmation screen based on the video display period.