Range-finding device and imaging apparatus

A range-finding device (3) includes a plurality of image pickup units (22a, 22b, 22c) disposed at a predetermined interval with each other, a lens unit (L) to form subject images of a subject on the plurality of image pickup units, the image pickup units on which the subject image is formed outputting signals of the subject image, and a distance calculation unit (24) to calculate a distance to the subject based on the signals output from the image pickup units. The plurality of image pickup units are formed on a single substrate. The subject image is formed through the lens unit on at least two image pickup units of the plurality of image pickup units. The distance calculation unit calculates a distance to the subject based on the signals output from the at least two image pickup units on each of which the subject image is formed.