An abnormality detection device (100) comprises an image acquisition unit (11), a motion extraction unit (12), a weighting unit (13), a scattering degree calculation unit (14), and a detection unit (15). The image acquisition unit (11) acquires a plurality of images from a camera (200). The motion extraction unit (12) extracts, from a plurality of moving bodies included in the image in one frame, a plurality of motion vectors determined by the magnitude of a motion and the direction of the motion. The weighting unit (13) calculates an occurrence probability for each motion vector of the plurality of motion vectors, and weights the occurrence probabilities. The scattering degree calculation unit (14) calculates the degree of scattering in the one frame on the basis of the weighted occurrence probabilities. The detection unit (15) compares the degree of scattering to a threshold value, and detects abnormalities on the basis of the comparison results.
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