PURPOSE: To improve measurement accuracy and to simplify the measurement by alkylating the thiol group remaining in liposome immobilized with an antigen, antibody or a part of the antibody.

CONSTITUTION: Desired phospholipid, glycolipid or fatty acid and the reagent such as thiol carboxylic acid are brought into reaction in a solvent to introduce the thiol group into the phospholipid molecules, etc. A thin film of lipid is formed on the wall surface of a flask when a proper amt. of the resalted phospholipid, glycolipid or fatty acid contg. the thiol group or either of the phospholipid and the glycolipid is put into the flask and a solvent is added thereto and the solvent is sucked and removed to dry the same after dissolving and mixing. The liposome liquid suspension and the antigen, the antibody or a part of the antibody are then brought into reaction in a suitable buffer soln. to immobilize the antigen, the antibody or a part of the antibody to the liposome. Further, the alkyl halide group-contg. compd. is brought into reaction with the thiol group remaining on the liposome to alkylate the same after the antigen, the antibody or a part of the antibody is immobilized to the liposome.