A surface shape measuring apparatus includes an illumination system and a light receiving system. The illumination system splits wide-band light from a light source into measurement light and reference light, illuminates the measurement light to obliquely enter a surface of the film, and illuminates the reference light to obliquely enter a reference mirror. The light receiving system combines the measurement light reflected by the surface of the film and the reference light reflected by the reference mirror with each other and introduces the combined light to a photoelectric conversion element. An incident angle of the measurement light upon the surface of the film and an incident angle of the reference light upon the reference mirror are each larger than the Brewster's angle. S-polarized light and p-polarized light included in the measurement light entering a surface of the substrate have equal intensity on the photoelectric conversion element.