Abstract: An anomaly detection device includes: an initial-stage detection information acquisition unit that acquires detection information at an initial stage in a series of a machining step performed using one tool; a map-function identification unit that identifies a mapping function for mapping the detection information at the initial stage, on reference detection information; a wear-progress-stage detection information acquisition unit that acquires detection information at a wear progress stage that follows the initial stage in the series of the machining step; a map-function application unit that applies the mapping function to the detection information at the wear progress stage; an anomaly-degree calculation unit that calculates an anomaly degree indicating a degree of difference, from the reference detection information, of the detection information at the wear progress stage to which the mapping function is applied; and an anomaly detecting unit that detects an abnormality of the tool based on determination