PURPOSE: To obtain a stable lipid bimolecular membrane without requiring a solution system for holding the lipid bimolecular membrane by coating both surfaces of a membrane with a polymer gel having a surface made hydrophilic.

CONSTITUTION: A polymer gel 1 is prepared by copolymerizing isopropylacrylamide and sodium acrylate. Next, a bimolecular membrane 2 of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-L-α-dipalmitoyl-phosphatidylethanolamine being phospholipid having a dye probe is formed to the surface of the polymer gel 1. Subsequently, this bimolecular membrane 2 is held in air in this state to bond the polymer gel 1 to the bimolecular membrane 2.