Angular　distribution　and　spin　polarization　of　photoelectrons　from　3s　valence　subshell　of　neutral　magnesium　are　investigated　by　using　the　multiconfiguration　relativistic　random-phase　approximation.　Photoionization　parameters　for　all　five　Rydberg　series　of　double-excitation　resonances　(3p　ns)P-1,3(1)o,　(3p　nd)P-1,3(1)o,　and　(3p　nd)D-3(1)o　between　the　Mg+[3s]　and　Mg+[3p]　thresholds　are　presented　to　clarify　the　high-energy　portion　of　the　Rydberg　series,　in　which　peaks　corresponding　to　double　excitations　can　be　identified　unambiguously.