A porous hollow-fiber membrane was modified with diethylamino (DEA) and ethanolamino (EA) groups by radiation-induced graft polymerization and subsequent chemical modifications. Adsorption behavior of bovine serum albumin (BSA) was investigated by permeating a BSA buffer solution through the membrane. A polymer chain grafted onto the pore surface of the membrane held BSA in multilayers, i.e., three-dimensionally in a tentacle-like manner. The membrane with a DEA group density of 2.5 mol/kg had a binding capacity for BSA of 443 g/kg, equivalent to 11 times the monolayer adsorption. Permeation of a buffer solution containing 0.5 M NaCl as an eluent caused the graft chain to shrink, resulting in restricted diffusion of BSA departing from the graft chain toward the pore interior while realizing a quantitative elution. Hydrodynamic analysis of the change in permeation pressure accompanying BSA binding to the graft chain showed that the BSA molecules layered in the graft chains form a closely packed structure.