To provide a transmission wavefront measuring method of a birefringence optical element measuring properly a transmission wavefront, even when imaging an interference fringe having a domain where transmission wavefront information is not carried correctly by an influence of birefringence carried by a test optical element.

Each interference fringe is imaged relative to each of a plurality of imaging arrangement positions set so that a relative position relation between a direction of a plane of polarization of measuring light and the test optical element is mutually different, and improper domains A1, A2 where the transmission wavefront information is not carried correctly are specified in each imaged interference fringe. Each wavefront shape information in other domains excluding the improper domains A1, A2 is linked mutually by a synthetic aperture method to determine wavefront shape information of the whole transmission wavefront area, and an aberration of the transmission wavefront is determined based on the wavefront shape information of the whole transmission wavefront area.