A coordinate calculating apparatus for calculating two object position coordinate points from an image captured by an image capturing apparatus, wherein the image capturing apparatus is configured to capture the image such that the image includes object images of two predetermined target objects placed at a distance from the image capturing apparatus, and the two object position coordinate points indicating positions of the two predetermined target objects on the captured image, the apparatus comprising: coordinate detecting means of detecting, in the captured image, one or more areas satisfying a predetermined condition for detection of the object images, and of detecting, for each of the one or more areas, a position coordinate point of the area; characterized in that the apparatus further comprises: reference setting means (10,S35;S75) of setting a reference in a previously captured image with respect to at least one of a direction connecting two reference position coordinate points and a length between the two reference position coordinate points; and selection means (10,S81) of, when a plurality of position coordinate points in the captured image are detected by the coordinate detecting means, with respect to all combinations of two selected position coordinate points among the plurality of position coordinate points, comparing at least one of a direction connecting the two selected position coordinate points in the combinations and a length between the two selected position coordinate points, with the reference, and selecting a combination of the two selected position coordinate points in the combinations most close to the reference as the two object position coordinate points. coordinate detecting means of detecting, in the captured image, one or more areas satisfying a predetermined condition for detection of the object images, and of detecting, for each of the one or more areas, a position coordinate point of the area; characterized in that the apparatus further comprises: reference setting means (10,S35;S75) of setting a reference in a previously captured image with respect to at least one of a direction connecting two reference position coordinate points and a length between the two reference position coordinate points; and selection means (10,S81) of, when a plurality of position coordinate points in the captured image are detected by the coordinate detecting means, with respect to all combinations of two selected position coordinate points among the plurality of position coordinate points, comparing at least one of a direction connecting the two selected position coordinate points in the combinations and a length between the two selected position coordinate points, with the reference, and selecting a combination of the two selected position coordinate points in the combinations most close to the reference as the two object position coordinate points. reference setting means (10,S35;S75) of setting a reference in a previously captured image with respect to at least one of a direction connecting two reference position coordinate points and a length between the two reference position coordinate points; and selection means (10,S81) of, when a plurality of position coordinate points in the captured image are detected by the coordinate detecting means, with respect to all combinations of two selected position coordinate points among the plurality of position coordinate points, comparing at least one of a direction connecting the two selected position coordinate points in the combinations and a length between the two selected position coordinate points, with the reference, and selecting a combination of the two selected position coordinate points in the combinations most close to the reference as the two object position coordinate points.