An immobilized metal affinity porous membrane of a hollow-fiber form was applied to the purification of geneticallyengineered histidine (His)–tagged fusion protein. An iminodiacetate (IDA)group (–N(CH2COOH)2)was introducedinto the poly–glycidyl methacrylate chain grafted onto a polyethylene-made porous hollow–fiber membrane.Subsequently, nickel ions were bound to the IDA group before the permeation of a His–tagged green fluorescent pro-tein (GFP)solution through the porous membrane. The resultant immobilized nickel affinity porous membrane(immobilized Ni membrane)had a ligand density of 0.36 mol/kg and a phosphate buffer flux of 0.4 m/h at a perme-ation pressure of 0.1 MPa and 298 K. His–tagged GFP adsorbed to the immobilized Ni membrane was eluted by per-meating a 0.5 M imidazole solution through the porous membrane. From an SDS–PAGE analysis, the purity of theprotein was found to be improved from 35 to 97%.