1. A stereo camera device detecting a distance to a moving subject, the stereo camera device comprising: two cameras that are installed and separated from each other by a base line length on a moving platform; and circuitry configured to calculate distances to the moving subject on images based on the images acquired by the two cameras; wherein the circuitry is configured to search for corresponding points of the images acquired by the two cameras and to calculate two parallaxes, based on differences in positional coordinates of the corresponding points on the images, at least at two time points, wherein the circuitry is configured to calculate a running distance, that is a difference between the distances to the moving subject at the two time points, based on relative velocities of the two cameras with respect to the moving subject, wherein the circuitry is configured to calculate parallax offset values of the corresponding points across the images using the two parallaxes calculated by the circuitry at least at the two time points and using the calculated running distance, and wherein the circuitry is configured to perform a statistical analysis on a distribution of the parallax offset values and determine an optimum value of the parallax offset values, the optimum value being used as a correction parameter.