A range finding device of a construction, in which, at the time of receiving first and second images of an object to be formed by a range finding optical system with a relative positional parallax corresponding to the object distance into first and second photoelectric light receiving elements, respectively, these images are shifted on the light receiving surfaces of the respective first and second light receiving elements by a vibrating optical device at a same cycle and same phase to thereby scan these first and second images by the first and second light receiving elements; image scanning signals on the first and second images to be obtained at this time are converted into digital values; thereafter, these values are stored in the first and second storing devices where the coincidence and non-coincidence of these digitalized image scanning signals are detected by means of a coincidence detecting device, while one of these image scanning signals are relatively shifted bit by bit with respect to other image scanning signals; and the shift bit quantitites required until the image scanning signals of the same bit numbers of these first and second images may become optimumly coincided, thereby finding out the object distance from the shift bit quantities at the time.