A stereo ranging apparatus adapted to calculate the distance to a target using a first image and a second image of the target, the apparatus comprising: a filter storage section adapted to store blur adjusting filter coefficients corresponding to combinations of image heights of the first image and image heights of the second image; a blur adjusting section adapted to acquire, for each of a plurality of second partial images, a blur adjusting filter coefficient that corresponds to a combination of an image height of a first partial image and an image height of the second partial image from the filter storage section, and to adjust the blur of one partial image with the lower image height of the first partial image and the second partial image to the blur of the other partial image with the higher image height, using the acquired blur adjusting filter coefficient, the first partial image being an image of the target in the first image, the second partial image being a candidate for an image of the target in the second image; a disparity measuring section adapted to calculate, for each of the plurality of second partial images, the dissimilarity between the partial image with the adjusted blur among the first partial image and the second partial image and the partial image with the unadjusted blur among the first partial image and the second partial image, to determine the second partial image having the least dissimilarity among the plurality of second partial images as the image of the target in the second image, and to measure disparity between the first partial image and the second partial image which has been determined as the image of the target in the second image; and a distance calculation section adapted to calculate the distance to the target based on the disparity. a filter storage section adapted to store blur adjusting filter coefficients corresponding to combinations of image heights of the first image and image heights of the second image; a blur adjusting section adapted to acquire, for each of a plurality of second partial images, a blur adjusting filter coefficient that corresponds to a combination of an image height of a first partial image and an image height of the second partial image from the filter storage section, and to adjust the blur of one partial image with the lower image height of the first partial image and the second partial image to the blur of the other partial image with the higher image height, using the acquired blur adjusting filter coefficient, the first partial image being an image of the target in the first image, the second partial image being a candidate for an image of the target in the second image; a disparity measuring section adapted to calculate, for each of the plurality of second partial images, the dissimilarity between the partial image with the adjusted blur among the first partial image and the second partial image and the partial image with the unadjusted blur among the first partial image and the second partial image, to determine the second partial image having the least dissimilarity among the plurality of second partial images as the image of the target in the second image, and to measure disparity between the first partial image and the second partial image which has been determined as the image of the target in the second image; and a distance calculation section adapted to calculate the distance to the target based on the disparity.