A detecting apparatus for detecting displacement of a bearing unit sandwiched between a spindle extending in an axial direction and a spindle seat is provided. The detecting apparatus includes a detector unit and a control unit. The detector unit includes a pair of sensing devices with each sensing device including a sensor that abuts against an end surface of an outer ring of the bearing unit and outputting, based on a sensing of the sensor thereof, a detected signal associated with a displacement of the end surface in the axial direction. The control unit is configured to determine whether the bearing unit is abnormal based on the detected signals.