To provide a method for efficiently producing a structure- discriminating protein which discriminates a native protein from a denatured one.

This is a method for producing a structure-discriminating protein which recognizes a protein 1 having normal structure to bind, but does not recognize a protein having abnormal structure. The structure-discriminating protein is isolated by (1) applying a phase display library containing a phase which displays a structure-discriminating protein to affinity chromatography using gel 6a which was coupled to the protein 1 having normal structure, (2) eluting a fraction 5a which adsorbed onto gel 6a, (3) applying the fraction 5a to affinity chromatography using gel which was coupled to the protein having abnormal structure, (4) selecting a phase having an activity to bind the protein 1 having normal structure from passed fractions, (5) releasing the structure- discriminating protein from the phase, followed by (6) selecting the structure- discriminating protein.