An object detection system is provided with radar detection means (2), image detection means (3), and collating means (4). The collating means (4) detects a combination of an object detected by the radar detection means (2) and an object selected among those detected by the image detection means (3), which is the closest to the object detected by the radar detection means (S1, S2), detects a combination of an object detected by the image detection means (3) and an object selected among those detected by the radar detection means (2), which is the closest to the object detected by the image detection means (S3, S4), and determines when there is a coincidence between the combination of the object detected by the radar detection means (2) and the selected object as being closest thereto and the combination of the object detected by the image detection means (3) and the selected object as being closest thereto, that the object detected by the radar detection means (2) is the same as the object detected by the image detection means (S5).