The present invention provides an RO membrane or FO membrane which exhibits salt suppression performance at a high water permeation quantity and which is constituted from a covering layer which comprises a phospholipid bilayer formed on a surface of a porous membrane main body, the RO membrane or FO membrane being a permselective membrane having a porous membrane having a pore diameter of 5-50 nmand a covering layer which comprises a phospholipid bilayer and which is formed on a surface of the porous membrane, wherein (i) the phospholipid bilayer contains a phospholipid, amphotericin B and ergosterol, (ii) the content of the amphotericin B is 3-20 mol.% relative to the phospholipid bilayer, and (iii) the overall content of ergosterol and amphotericin B in the phospholipid bilayer is 10-30mol.%.