A camera [[17]] captures an image by applying for every frame camera control values that are computed for a white line detection, and captures the image by applying for every frame camera control values that are computed for a three-dimensional object detection. The captured frame is transmitted to a stereo ECU [[20]] by adding thereto a frame counter value and the camera control values that were applied when capturing the image, and the stereo ECU [[20]] distinguishes the frame for white line from the frame for three-dimensional object depending on the added frame counter value. Based on the distinguished frame, the stereo ECU [[20]] carries out the white line detection or the three-dimensional object detection, computes the camera control values for the white line or the camera control values for the three-dimensional object, and transmits the computed camera control values to the camera [[17]].