A two-eyed type optical distance measuring apparatus operable in accordance with a phase difference detecting process to optically measure a distance between the apparatus and an object to be measured is disclosed. To determine the distance between the apparatus and the object to be measured, a phase difference between the phase of a reflected light beam reflected from the object to be measured and the optical phase of a reference light beam derived from partial division of a distance measuring light beam emitted from a light source is detected and calculated. The apparatus includes as essential components a light source disposed in a housing on the light emitting side to emit a modulated distance measuring light beam therefrom toward the object to be measured, a light emitting element in a housing on the light receiving side and a reference light introducing mechanism for introducing a part of the modulated distance measuring light beam emitted from the light source into the light receiving element via an optical fiber. To prepare the reference light beam, a shade is arranged at the intermediate part of the housing on the light emitting side. In addition, an iris mechanism is disposed on the incident side of the optical fiber to variably adjust an optical quantity of the reference light beam.
