To obtain an apparatus and a method for measuring a window face distortion in order for measuring and correcting a wavefront aberration because of the distortion generated by a pressure of a flight wind or a temperature difference to the window face set to an aircraft optical antenna or the like.

There are provided modulating means 2 for modulating a light intensity of light generated from each of light sources 1, a small aperture part 3 for emitting the light from spatially different positions, an optical system 4 for irradiating the light to the window face 11 to be measured, a condenser lens 5 for collecting the light affected by the distortion of the window face 11, detecting means 6a and 6b for detecting a light intensity of the collected light, demodulating means 7a and 7b for demodulating detected light intensity signals, a signal-operating means 8 for calculating a wavefront inclination and the wavefront aberration generated by the distortion of the window face 11 with the use of demodulation signals, a light propagation direction variable means 9 for changing an advance direction of the light, and a control means 10 for controlling the light propagation direction variable means 9 on the basis of the operated result by the signal-operating means 8.