1. A location measuring device comprising: a feature point extracting section for extracting a plurality of feature points on a photographing object from each of successively photographed images in a plurality of frames obtained with an image obtaining means, a location of the image obtaining means relatively varying to a location of the photographing object with time; a feature point tracking section for searching each of the successively photographed images for points corresponding to the feature points and tracking the feature points; a first relative orientation process section for choosing one photographed image frame and another photographed image frame from tracked results of the feature point tracking section, carrying out relative orientation based on a plurality of points randomly chosen out of the respective corresponding points between the two photographed image frames, determining vertical parallaxes, applying robust estimation to the determined vertical parallaxes, and determining estimated values of parameters for the relative orientation while reducing influence of errors; a second relative orientation process section for carrying out relative orientation between the respective corresponding points of the two image frames based on the parameters for the relative orientation estimated in the first relative orientation process section, calculating vertical parallaxes of the feature points, applying threshold process to the vertical parallaxes, and excluding incorrect corresponding points or determining appropriateness of the photographed image frames; and a location measuring section for measuring a coordinate of the photographing object, or the location or a photographing posture of the image obtaining means using the plurality of photographed image frames.