One-handed helical poly(substituted phenylacetylene) having aldehyde groups has been newly synthesized in the membrane state by deprotection reaction of the corresponding poly(substituted phenylacetylene) having dioxolane groups. The permeability of phenylethylamine racemate ((RS)-PEA) of the deprotected membrane showed about five times higher together with the increase of enantioselectivity than that of the corresponding polymer membrane without aldehyde groups. The better performance was attributed to the enantioselective reaction between the aldehyde groups of the membrane with the amino groups in the permeant during the concentration-driven permeation of (RS)-PEA.