An electrophotographic developing member comprising: a substrate having an electroconductive outer surface; an electrically insulating resin layer on the electroconductive outer surface of the substrate ; and electrically insulating domains on an outer surface of the electrically insulating resin layer , the electrophotographic developing member having an outer surface including a surface of the electrically insulating resin layer and surfaces of the electrically insulating domains , wherein the surfaces of the electrically insulating domains constituting the outer surface of the developing member and the surface of the electrically insulating resin layer constituting the outer surface of the developing member are configured to, when electrically charged, generate a difference in potential between the electrically insulating domains and the electrically insulating resin layer , wherein the difference in potential is specified in that when the surfaces of the electrically insulating domains are electrically charged so as to have potential of V 0 (V), a potential decay time constant defined as a period of time necessary for decaying from V 0 (V) to VO× (1/e) (V) is 60.0 seconds or longer, and when the surface of the electrically insulating resin layer is electrically charged so as to have a potential of V 0 (V), a potential decay time constant defined as a period of time necessary for decaying from V 0 (V) to V 0 × (1/e) (V), is shorter than 6.0 seconds, and wherein assuming that the electrically insulating domains are independent from each other and are orthographically projected onto the electroconductive outer surface of the substrate , to obtain projection images of the respective electrically insulating domains , each of areas of the projection images is defined as S, and each of areas of convex envelopes of the projection images is defined as H, at least 20% by number of the electrically insulating domains satisfy the relationship represented by Expression : 0.05 ≤ S / H ≤ 0.80 . a substrate having an electroconductive outer surface; an electrically insulating resin layer on the electroconductive outer surface of the substrate ; and electrically insulating domains on an outer surface of the electrically insulating resin layer , the electrophotographic developing member having an outer surface including a surface of the electrically insulating resin layer and surfaces of the electrically insulating domains , wherein the surfaces of the electrically insulating domains constituting the outer surface of the developing member and the surface of the electrically insulating resin layer constituting the outer surface of the developing member are configured to, when electrically charged, generate a difference in potential between the electrically insulating domains and the electrically insulating resin layer , wherein the difference in potential is specified in that when the surfaces of the electrically insulating domains are electrically charged so as to have potential of V 0 (V), a potential decay time constant defined as a period of time necessary for decaying from V 0 (V) to VO× (1/e) (V) is 60.0 seconds or longer, and when the surface of the electrically insulating resin layer is electrically charged so as to have a potential of V 0 (V), a potential decay time constant defined as a period of time necessary for decaying from V 0 (V) to V 0 × (1/e) (V), is shorter than 6.0 seconds, and wherein assuming that the electrically insulating domains are independent from each other and are orthographically projected onto the electroconductive outer surface of the substrate , to obtain projection images of the respective electrically insulating domains , each of areas of the projection images is defined as S, and each of areas of convex envelopes of the projection images is defined as H, at least 20% by number of the electrically insulating domains satisfy the relationship represented by Expression : 0.05 ≤ S / H ≤ 0.80 . <EOS>