An object detection apparatus applied to a vehicle having a sensor unit mounted on a predetermined member provided to the vehicle, the sensor unit being provided with an object detection sensor that detects position information of an object present around the vehicle and a tilt sensor that detects a tilt angle as inclination with respect to a predetermined direction, and performing a process of detecting the object based on the position information of the object detected by the object detection sensor, the object detection apparatus comprising a detachment state determination section that determines a detachment state of the predetermined member based on the tilt angle detected by the tilt sensor.