A stereo camera device with a left and right imaging portion (105, 106) for imaging a range located ahead of a subject vehicle comprising a road-shoulder detecting device for detecting a road-shoulder which is a boundary between a vehicular road surface and an off-road region which comprises: a distance information calculating portion adapted to calculate presence or absence of a physical object and, in case the object is present, calculate a distance from a subject vehicle to the object from input three-dimensional image information about left and right images of an environment outside of the subject vehicle taken by the left imaging portion and the right imaging portion and to output a distance image representing the distance from the subject vehicle to the object; a vehicular road surface detecting portion adapted to detect the vehicular road surface traveled by the subject vehicle from the distance image based on the calculated distance; a height difference calculating portion adapted to measure a height difference between the detected vehicular road surface and the off-road region; characterized in that said vehicular road surface detecting portion has a three-dimensional information calculation processing portion adapted to calculate three-dimensional positions of pixels from the distance image based on the distance calculated by said distance information calculating portion and a vehicular road equation application processing portion for extracting pixels that are considered to be the vehicular road surface based on the calculated three-dimensional positions and detecting the vehicular road surface; wherein said height difference calculating portion is adapted to measure the height difference between said vehicular road surface and the off-road region based on the three-dimensional positions calculated by said three-dimensional information calculation processing portion and on the vehicular road surface detected by said vehicular road surface equation application processing portion; wherein the stereo camera device further comprises a road shoulder decision portion adapted to extract off-road regions lower than said vehicular road surface based on said height difference, extract contour elements regarding all pixels within the extracted off-road regions, take the extracted contour elements as contour lines of the off-road regions, and judge from the contour lines road shoulders occurring in a case where off-road regions are lower than the vehicular road surface, and a vehicle departure decision portion adapted to make a decision as to whether or not the subject vehicle will run off the road based on the result of the decision made by the road shoulder decision portion, on a detected speed and on a steering angle of the subject vehicle. a distance information calculating portion adapted to calculate presence or absence of a physical object and, in case the object is present, calculate a distance from a subject vehicle to the object from input three-dimensional image information about left and right images of an environment outside of the subject vehicle taken by the left imaging portion and the right imaging portion and to output a distance image representing the distance from the subject vehicle to the object; a vehicular road surface detecting portion adapted to detect the vehicular road surface traveled by the subject vehicle from the distance image based on the calculated distance; a height difference calculating portion adapted to measure a height difference between the detected vehicular road surface and the off-road region; characterized in that said vehicular road surface detecting portion has a three-dimensional information calculation processing portion adapted to calculate three-dimensional positions of pixels from the distance image based on the distance calculated by said distance information calculating portion and a vehicular road equation application processing portion for extracting pixels that are considered to be the vehicular road surface based on the calculated three-dimensional positions and detecting the vehicular road surface; wherein said height difference calculating portion is adapted to measure the height difference between said vehicular road surface and the off-road region based on the three-dimensional positions calculated by said three-dimensional information calculation processing portion and on the vehicular road surface detected by said vehicular road surface equation application processing portion; wherein the stereo camera device further comprises a road shoulder decision portion adapted to extract off-road regions lower than said vehicular road surface based on said height difference, extract contour elements regarding all pixels within the extracted off-road regions, take the extracted contour elements as contour lines of the off-road regions, and judge from the contour lines road shoulders occurring in a case where off-road regions are lower than the vehicular road surface, and a vehicle departure decision portion adapted to make a decision as to whether or not the subject vehicle will run off the road based on the result of the decision made by the road shoulder decision portion, on a detected speed and on a steering angle of the subject vehicle.