A wavefront measuring device is disclosed which is capable of measuring an average wavefront and the retardation of a lens including birefringence. The measuring device includes a light source for emitting a linearly polarized light; a polarization orientation setting member for switching the polarization orientation of the light flux from the light source between at least two orientations; a light synthesizing member for synthesizing the light flux after passing the light fluxes through an object to be measured and a reference surface; an analyzer for switching the polarization orientation so as to pass only the same polarized component as the polarized light incident on the object to be measured; an image pickup member for detecting interference information of the light flux obtained through the analyzer; and a calculating section for calculating the average wavefront and/or the retardation of the object to be measured.
