A light-interference measuring apparatus adapted to measure a three-dimensional shape, comprising: a light source to output a broad band light; an objective lens section to branch an optical path of the broad band light output from the light source into a reference optical path including a reference mirror and a measuring optical path including a measuring object (w), and to output a superposed wave of a reference light reflected by the reference mirror and an object light reflected by the measuring object (w); an optical path length changing section to change an optical path length of either of the reference optical path or the measuring optical path; and an imaging section to form an interference image data of the superposed wave output from the objective lens section, wherein the objective lens section includes; a phase difference control member to control a phase difference between the reference light and the object light to generate destructive interference fringes at a position at which an optical path difference between the reference optical path and the measuring optical path is zero, and a minimum luminance position detecting section to detect minimum luminance position of the destructive interference fringes based on the interference image data formed by the imaging section; wherein the optical path length changing section is adapted to change the optical path length of either the reference optical path or the measuring optical path to the position at which the minimum luminance position is detected by the minimum luminance portion detecting section, whereby the optical path difference between the reference optical path and the measuring optical path becomes zero; and wherein either the objective lens section includes a beam splitter to branch the optical path of the broad band light output from the light source into the reference optical path and the measuring optical path; the phase difference control member is attached to the beam splitter; and a light passing through the measuring optical path transmits through the phase difference control member twice and thereby a phase of the transmitted light is reversed by 180°; or in the objective lens section: the phase difference control member is arranged at a reflection surface side of the reference mirror; and a light passing through the reference optical path transmits through the phase difference control member twice before and after being reflected by the reference mirror and thereby a phase of the light is reversed by 180°. a light source to output a broad band light; an objective lens section to branch an optical path of the broad band light output from the light source into a reference optical path including a reference mirror and a measuring optical path including a measuring object (w), and to output a superposed wave of a reference light reflected by the reference mirror and an object light reflected by the measuring object (w); an optical path length changing section to change an optical path length of either of the reference optical path or the measuring optical path; and an imaging section to form an interference image data of the superposed wave output from the objective lens section, wherein the objective lens section includes; a phase difference control member to control a phase difference between the reference light and the object light to generate destructive interference fringes at a position at which an optical path difference between the reference optical path and the measuring optical path is zero, and a minimum luminance position detecting section to detect minimum luminance position of the destructive interference fringes based on the interference image data formed by the imaging section; wherein the optical path length changing section is adapted to change the optical path length of either the reference optical path or the measuring optical path to the position at which the minimum luminance position is detected by the minimum luminance portion detecting section, whereby the optical path difference between the reference optical path and the measuring optical path becomes zero; and wherein either the objective lens section includes a beam splitter to branch the optical path of the broad band light output from the light source into the reference optical path and the measuring optical path; the phase difference control member is attached to the beam splitter; and a light passing through the measuring optical path transmits through the phase difference control member twice and thereby a phase of the transmitted light is reversed by 180°; or in the objective lens section: the phase difference control member is arranged at a reflection surface side of the reference mirror; and a light passing through the reference optical path transmits through the phase difference control member twice before and after being reflected by the reference mirror and thereby a phase of the light is reversed by 180°.