1. A range finder for finding a range to a target by image realization comprising: a first and a second imaging device arranged at a predetermined interval; a pattern extracting section for extracting a first pattern having a predetermined size and the first positional information from a first image of the target which has been made by the first imaging device; a correlation processing section for detecting a second pattern having the second positional information, which is most correlated with the first pattern, from a plurality of horizontal or vertical lines located at positions corresponding to the first positional information in the second image of the target which has been made by the second imaging device; and a parallax calculating section for finding parallax from the first and the second positional information.