1. An image angle variation detection device comprising: an image angle variation detection unit which detects an image angle variation of an imaging device from videos shot by the imaging device based on fixed point information including the position of a fixed point specified by an image angle of the imaging device and the features indicating the characteristics of the fixed point; and a situation determination unit which determines that the image angle of the imaging device is varied when a change in the image angle variation is stable for a certain period of time.