The wavefront aberration measuring method includes measuring an intensity distribution of a measuring light transmitted through or reflected by an object to be measured, by using a light-receiving sensor, calculating a first differential wavefront which is a differential wavefront of the measuring light on the light-receiving sensor, and calculating a second differential wavefront by performing a correction process on the first differential wavefront depending on an incident angle of the measuring light to the light-receiving sensor. The method further includes calculating a wavefront aberration of the object by using the second differential wavefront.