In an object detection apparatus, a first trajectory estimation unit estimates a trajectory of a first object detected by an electromagnetic wave sensor. An optical flow acquisition unit image-processes a captured image acquired from a camera to acquire movement directions based on optical flows of feature points in the captured image. A movement direction match determination unit determines whether or not a match occurs between a movement direction based on the optical flows and a movement direction based on the trajectory of the first object. If a match occurs between the movement direction based on the optical flows of the plurality of feature points and the movement direction based on the trajectory of the first object, a sameness determination unit determines that a second object identified by the plurality of feature points and the first object are a same object.