JP 5812064 B discloses an object recognition device which is configured to determine whether or not a first object and a second object are the same object.  The first object is detected by a millimeter wave radar.  The second object is detected by an in-vehicle camera.  When an area centered on the position of the first object and an area centered on the position of the second object are overlapped, it is determined that the two objects are the same object. 
In the object recognition device described above, an error based on the characteristics of millimeter wave radar is taken into consideration in the area centered on the position of the first object.  In addition, an error based on the characteristics of the in-vehicle camera is taken into consideration in the area centered on the position of the second object.  However, since these regions are fixed in a relative direction of the detected objects, there is a possibility of erroneously determining that different objects detected in a curved lane are the same object. 
Specifically, when a leading vehicle (i.e., the first object) traveling on a curved lane ahead of the vehicle equipped with the object recognition device and another leading vehicle (i.e., the second object) traveling on a curved lane next to the curved lane on which the first object travels are detected in the same relative direction, these vehicles may be erroneously determined to be the same object.  The same is true when the leading vehicle (i.e., the first object) and a roadside object adjacent to the leading vehicle (i.e., the second object) such as a guard rail or a retaining wall are detected in the same relative direction.  Therefore, it is desirable to improve for preventing an occurrence of such erroneous determination from occurring. 
The present disclosure addresses the above described problem, and an object of the present disclosure is, to provide a technique capable of preventing an occurrence of an erroneous determination that different objects detected around a curved lane are the same object.