An abnormality detection apparatus includes a feature extraction unit configured to extract an image feature according to a common algorithm, a flow calculation unit, a first abnormality detection unit, and a second abnormality detection unit. An extraction range for the image feature is composed of a predetermined first partial area in a first image, a predetermined second partial area in a second image, and areas near places in the first and second images predicted as destinations of the feature point. The first abnormality detection unit detects an abnormality in the first (second) image based on an optical flow for a feature point in the first (second) partial area. The second abnormality detection unit detects an abnormality by using a feature point in a first overlapped extraction area defined in a first overlapped area and a feature point in a second overlapped extraction area defined in a second overlapped area.