A traveling road surface detection device that detects a traveling road surface based on disparity information obtained from a captured image around a vehicle captured by an in-vehicle camera, the device comprising: a three-dimensional position restoration unit configured to divide the captured image into a plurality of image areas; a traveling road surface determination unit configured to determine whether image areas into which the captured image is divided are each the traveling road surface based on the disparity information; wherein the traveling road surface is a road surface on which the vehicle can travel, the device further characterised in that it comprises: a traveling road surface interpolation unit configured to interpolate a first image area into a detected traveling road surface based on brightness information of the captured image, the first image area being included in interpolation candidates among the image areas not determined to be the traveling road surface by the traveling road surface determination unit, wherein each of the image areas is divided into a plurality of pixel ranges composed of a plurality of pixels, wherein the plurality of pixel ranges are each smaller than the respective image areas, and wherein each of the plurality of pixel ranges includes the same number of pixels and has the same shape in all of the image areas, and the first image area is an image area in which a number of first pixel ranges is equal to or larger than a second threshold, or a ratio of the first pixel ranges to all pixel ranges of the first image area is equal to or larger than a third threshold, wherein each of the first pixel ranges is adjacent to a further pixel range and has a brightness that is different from the brightness of the further pixel range by at most a first threshold. a three-dimensional position restoration unit configured to divide the captured image into a plurality of image areas; a traveling road surface determination unit configured to determine whether image areas into which the captured image is divided are each the traveling road surface based on the disparity information; wherein the traveling road surface is a road surface on which the vehicle can travel, the device further characterised in that it comprises: a traveling road surface interpolation unit configured to interpolate a first image area into a detected traveling road surface based on brightness information of the captured image, the first image area being included in interpolation candidates among the image areas not determined to be the traveling road surface by the traveling road surface determination unit, wherein each of the image areas is divided into a plurality of pixel ranges composed of a plurality of pixels, wherein the plurality of pixel ranges are each smaller than the respective image areas, and wherein each of the plurality of pixel ranges includes the same number of pixels and has the same shape in all of the image areas, and the first image area is an image area in which a number of first pixel ranges is equal to or larger than a second threshold, or a ratio of the first pixel ranges to all pixel ranges of the first image area is equal to or larger than a third threshold, wherein each of the first pixel ranges is adjacent to a further pixel range and has a brightness that is different from the brightness of the further pixel range by at most a first threshold. a traveling road surface interpolation unit configured to interpolate a first image area into a detected traveling road surface based on brightness information of the captured image, the first image area being included in interpolation candidates among the image areas not determined to be the traveling road surface by the traveling road surface determination unit, wherein each of the image areas is divided into a plurality of pixel ranges composed of a plurality of pixels, wherein the plurality of pixel ranges are each smaller than the respective image areas, and wherein each of the plurality of pixel ranges includes the same number of pixels and has the same shape in all of the image areas, and the first image area is an image area in which a number of first pixel ranges is equal to or larger than a second threshold, or a ratio of the first pixel ranges to all pixel ranges of the first image area is equal to or larger than a third threshold, wherein each of the first pixel ranges is adjacent to a further pixel range and has a brightness that is different from the brightness of the further pixel range by at most a first threshold.