An object of the present invention is to provide a phase difference plate for an organic EL display device having excellent light resistance, an organic EL display device, and a method for producing a phase difference plate. The phase difference plate for an organic EL display device of an embodiment of the present invention is a phase difference plate for an organic EL display device having a phase difference layer formed from a composition containing a copolymer having both of a repeating unit A including a photo-alignment group and a repeating unit B including a moiety capable of expressing birefringence having reciprocal wavelength dispersion, in which the photo-alignment group includes a double bond structure of C═C or C═N.