There is provided a shape measuring apparatus using an interferometer comprising a lens for condensing temporarily light waves from a light source, and a light wave shaping plate having a pinhole with suitable size adapted to convert the condensed light waves into an ideal spherical wave and a window provided in the vicinity of the pinhole and having enough size to pass therethrough light wave surface information, in which at least one lens having a reference surface and a surface to be measured the optical axes of which are slightly decentered in an optical path of the light waves passed through the pinhole is arranged in a position where the light waves which are made incident perpendicularly to the reference surface to be reflected therefrom pass through the pinhole again, and the light reflected from the surface to be measured pass through the window, and the reflected light reflected by the reference surface to pass through the pinhole again and the reflected light reflected by the surface to be measured to pass through the window are made to interfere with each other to measure a shape of the surface to be measured.