Abstract: Provided is an abnormality detection device for a rotary wing unit. The rotary wing unit includes a plurality of rotary wings that is coaxially disposed. The abnormality detection device includes a controller configured to acquire at least one of a correlation at the time of normal operation between operation parameters related to the rotary wings and a correlation at the time of abnormal operation between the operation parameters and detect abnormality of the rotary wing unit, based on a correlation at the time of actual operation between the operation parameters and at least one of the correlation at the time of normal operation and the correlation at the time of abnormal operation.