Control determines whether or not two objects represent the same object, in which one object is detected at a first position in front of a vehicle by an electromagnetic wave sensor and the other object is detected at a second position in front of the vehicle by image sensor. The control further determines whether or not the other object is partially excluded from an image acquired by the image sensor, in which a part of the object may have been outside the imaging region of the image sensor. The control changes a determination condition used for determining whether or not the objects represent the same object, such that the object whose part is excluded from the acquired image is more easily determined as the same object, compared with an object determined that such a part is not excluded from the acquired image.