To provide a laser length measuring device capable of executing highly reliable and accurate distance measurement utilizing a self-coupling effect of a laser element by setting accurately a measuring reference point.

A non-reflection prevention treatment is applied only to one surface of, for example, a transparent cover for protecting the laser element or a transparent body comprising an optical fiber or the like for introducing a laser light from the laser element to a measuring object portion, which is provided on the front of the self-coupling type laser element for irradiating the wavelength modulated laser light subjected toward a measuring object, into which the laser light reflected by the measuring object is introduced. The surface of the transparent body to which the non-reflection prevention treatment is not applied is used as measuring reference point.