Method of Efficiently Screening Protein Capable of Specific Binding to Ligand

A method of selecting from a diversifying library at least one type of protein specifically binding to a ligand of interest, which comprises:

• (a) a step of allowing various types of proteins existing in said library to come into contact with the ligand of interest, incubating a mixture consisting of said group of proteins and the ligand of interest, and recovering a complex consisting of at least one type of protein and the ligand of interest;
• (b) a step of allowing at least several types of proteins selected in step (a) to come into contact with the ligand of interest, incubating a mixture consisting of said proteins and the ligand of interest, and confirming the binding ability of said proteins to the ligand of interest;
• (c) a step of allowing at least several types of proteins selected in step (a) to come into contact with one or two types of specific control ligand(s), incubating a mixture consisting of said proteins and the control ligand(s), and determining whether or not said proteins have bound to the control ligand(s);
• and
• (d) a step of selecting proteins, whose binding ability to the ligand of interest has been confirmed in step (b), and which have not bound to the control ligand(s) in step (c).