In a preparation stage, an abnormality detection device detects a first characteristic amount from each first frame contained in video data and stores the first characteristic amount in a storage unit. In an abnormality detection stage, the abnormality detection device detects a second characteristic amount from each second frame contained in video data obtained by imaging a work operation of the robot and stores the first characteristic amount in the storage unit. The abnormality detection device compares the second characteristic mount of the second frame and the first characteristic amount of each of the first frames and specifies the first characteristic amount that is the closest to the second characteristic amount. The abnormality detection device determines whether the work operation of the robot in the abnormality detection stage is abnormal on the basis of the specified first characteristic amount and the second characteristic amount.