An abnormality detection apparatus for detecting an abnormality of a ball screw provided in an injection molding machine includes a current sensor configured to detect an alternating current of a motor for applying a driving force to the ball screw; and a computation unit configured to detect an abnormality of the ball screw based on information related to a distribution of frequency components obtained by frequency analysis of an alternating current detected by the current sensor, and information related to a distribution of frequency components obtained by frequency analysis of an alternating current detected when the ball screw, which is normal, operates.