In the distance measuring device for an automatic focusing camera, the reliability is improved by preventing the device from electric noise, and the structure is simplified so as to provide interchangeability to reduce the production cost. A light receiving lens 2 and a multilayer printed circuit board 3 are mounted on a holder 1. A potting frame 6 is provided on the lens-facing side surface of the printed circuit board 3. An optical sensor 4 and an IC 5 are both mounted within a space 3 enclosed by the potting frame 6, and sealed by a protecting resin 7 simultaneously. Further, resistors S and capacitors C of a distance measuring circuit are mounted on the opposite surface of the printed circuit board 3. Both the surfaces of the printed circuit board 3 are connected to each other via a through hole to construct the distance measuring circuit. The protecting resin 7 transmits light having specified wave lengths. The light reflected from a subject to be photographed is received by the optical sensor 4 after passing through the protecting resin, and a distance to the subject is calculated on the basis of the received light data.