A method of screening for a protein-degradation inducing molecule, wherein the protein-degradation inducing molecule is a conjugate of a protein-degradation inducing tag and at least one protein binding molecule capable of binding to a target protein, the method including a step of selecting a molecule having an affinity with a protease without inhibiting degradation of a target protein by the protease from candidate molecules, wherein the protein-degradation inducing molecule can lead the target protein to degradation by the protease without ubiquitination of the target protein, wherein the method comprises the steps of i) preparing candidate molecules for a protein-degradation inducing tag, ii) immobilizing the candidate molecules on the well of a well plate, subjecting the immobilized candidate molecules to treatment with a protease labelled with a fluorochrome or a nucleic acid and selecting a molecule having an affinity with the protease based on the label on the protease, iii) selecting a candidate molecule which does not inhibit degradation of a target protein by the protease from the candidate molecules obtained in process step ii), iv) conjugating the candidate molecule obtained in process step iii) to at least one protein binding molecule capable of binding to the target protein to obtain a protein-degradation inducing molecule, v) introducing the protein-degradation inducing molecule to a system including the target protein, vi) selecting a protein-degradation inducing molecule which has induced degradation of the target protein, wherein the protease is a proteasome. wherein the protein-degradation inducing molecule can lead the target protein to degradation by the protease without ubiquitination of the target protein, wherein the method comprises the steps of i) preparing candidate molecules for a protein-degradation inducing tag, ii) immobilizing the candidate molecules on the well of a well plate, subjecting the immobilized candidate molecules to treatment with a protease labelled with a fluorochrome or a nucleic acid and selecting a molecule having an affinity with the protease based on the label on the protease, iii) selecting a candidate molecule which does not inhibit degradation of a target protein by the protease from the candidate molecules obtained in process step ii), iv) conjugating the candidate molecule obtained in process step iii) to at least one protein binding molecule capable of binding to the target protein to obtain a protein-degradation inducing molecule, v) introducing the protein-degradation inducing molecule to a system including the target protein, vi) selecting a protein-degradation inducing molecule which has induced degradation of the target protein, i) preparing candidate molecules for a protein-degradation inducing tag, ii) immobilizing the candidate molecules on the well of a well plate, subjecting the immobilized candidate molecules to treatment with a protease labelled with a fluorochrome or a nucleic acid and selecting a molecule having an affinity with the protease based on the label on the protease, iii) selecting a candidate molecule which does not inhibit degradation of a target protein by the protease from the candidate molecules obtained in process step ii), iv) conjugating the candidate molecule obtained in process step iii) to at least one protein binding molecule capable of binding to the target protein to obtain a protein-degradation inducing molecule, v) introducing the protein-degradation inducing molecule to a system including the target protein, vi) selecting a protein-degradation inducing molecule which has induced degradation of the target protein,