An on-vehicle image processor comprising: an imager mounted on a vehicle, which monitors circumference of the vehicle and captures images containing at least a road surface; a white line candidate area detector that detects a white line candidate area which is estimated to form a parking frame from the image imaged by the imager by detecting pixels constituting positive edges of the white line candidate area and pixels constituting negative edges of the white line candidate area, whereby a positive edge is determined if a difference in brightness values of two adjacent pixels in a predetermined direction is more than a predetermined value and the negative edge is determined if a difference in brightness values of two adjacent pixels, which are positioned in a predetermined distance from the positive edge and in a predetermined direction, is more than a predetermined value; an endpoint position detector that detects, from the detected white line candidate area, positions of two endpoints of a center line of the white line candidate area connecting middle points between the positive edge of the white line candidate area and the negative edge of the white line candidate area; a vehicle behavior measurer that measures a behaviour of the vehicle; an endpoint movement position predictor that predicts positions in the image where the two endpoints detected by the endpoint position detector are estimated to be moved during a predetermined time difference, based on the behaviour of the vehicle measured by the vehicle behavior measurer; an endpoint movement amount judger that obtains a difference between the positions of the endpoints predicted by the endpoint movement position predictor and positions of the endpoints detected by the endpoint position detector at the time when the time difference elapses and judges whether the difference is larger than a predetermined value; an endpoint position storage that stores the positions of endpoints before the movement, when the endpoint movement amount judger judges that the difference of the positions of the endpoints is larger than the predetermined value; a parking frame detector that detects a parking frame based on a position of the white line candidate area; and a distance calculator that calculates a distance between positions of endpoints detected by the endpoint position detector and the positions of the endpoints stored in the endpoint position storage, wherein, when the distance detected by the distance calculator is smaller than a predetermined value, the parking frame detector reduces a degree of contribution of the white line candidate area containing the endpoints detected by the endpoint position detector when the parking frame detector executes the detection of the parking frame. an imager mounted on a vehicle, which monitors circumference of the vehicle and captures images containing at least a road surface; a white line candidate area detector that detects a white line candidate area which is estimated to form a parking frame from the image imaged by the imager by detecting pixels constituting positive edges of the white line candidate area and pixels constituting negative edges of the white line candidate area, whereby a positive edge is determined if a difference in brightness values of two adjacent pixels in a predetermined direction is more than a predetermined value and the negative edge is determined if a difference in brightness values of two adjacent pixels, which are positioned in a predetermined distance from the positive edge and in a predetermined direction, is more than a predetermined value; an endpoint position detector that detects, from the detected white line candidate area, positions of two endpoints of a center line of the white line candidate area connecting middle points between the positive edge of the white line candidate area and the negative edge of the white line candidate area; a vehicle behavior measurer that measures a behaviour of the vehicle; an endpoint movement position predictor that predicts positions in the image where the two endpoints detected by the endpoint position detector are estimated to be moved during a predetermined time difference, based on the behaviour of the vehicle measured by the vehicle behavior measurer; an endpoint movement amount judger that obtains a difference between the positions of the endpoints predicted by the endpoint movement position predictor and positions of the endpoints detected by the endpoint position detector at the time when the time difference elapses and judges whether the difference is larger than a predetermined value; an endpoint position storage that stores the positions of endpoints before the movement, when the endpoint movement amount judger judges that the difference of the positions of the endpoints is larger than the predetermined value; a parking frame detector that detects a parking frame based on a position of the white line candidate area; and a distance calculator that calculates a distance between positions of endpoints detected by the endpoint position detector and the positions of the endpoints stored in the endpoint position storage, wherein, when the distance detected by the distance calculator is smaller than a predetermined value, the parking frame detector reduces a degree of contribution of the white line candidate area containing the endpoints detected by the endpoint position detector when the parking frame detector executes the detection of the parking frame.