A shape measuring apparatus includes: a light source; a two-beam interference objective lens; an imaging device; an observation optical system; a positioning device; and a control device. The control device calculates, for each unit region in the plurality of images obtained by the imaging device, as a focus position of the unit region, a position of the two-beam interference objective lens at which a luminance-based evaluation value is maximized over the plurality of images, and the control device measures a shape of a target object based on the focus position of each unit region in the plurality of images. The control device uses, as the evaluation value, a luminance of each unit region in the plurality of images as well as a value correlated with a difference between the luminance of the unit region and luminances of a plurality of unit regions adjacent to the unit region.