A road sensor system is provided which comprises at least one imaging sensor, an extraction means that captures brightness values for a plurality of windows corresponding to the area immediately in front of the vehicle from an image that is captured from the imaging sensor and is divided into a plurality of windows. It extracts a reference brightness value on the basis of the plurality of brightness values. The system includes a judgment means that compares the brightness value of at least one other window with the reference brightness value and judges that the window belongs to the road area if the difference is smaller than a predetermined value. The road area is determined by detecting the road surface based on brightness rather than the distance to the road surface.