A brake abnormality diagnosis device which diagnoses an abnormality in a brake of a brake-equipped motor provided in a robot or a machine tool, includes: an abnormality diagnosis unit which performs a diagnosis as to whether or not there is an abnormality in the brake, while the motor is excited and the brake is activated; and an output unit which, if it is diagnosed that there is an abnormality in the brake, notifies the abnormality in the brake without interrupting the excitation of the motor and without releasing the brake.