To provide a screening method and an identifying method, both for a ligand which has an affinity for a target substance and has structural change ability for forming a desired steric structure by connection with the target substance; a kit for performing both of the methods; and a sensor molecule by which the ligand is fluorescently-labeled.

The screening method includes the following steps: (a) a step for contacting a first mixture of candidate ligands including plural kinds of candidate ligands with a carrier having a structure recognition region for recognizing at least a part of a specified steric structure, followed by separating and collecting, as a second mixture of candidate ligands, a mixture of free candidate ligands not bound to the carrier; (b) a step for contacting the second mixture of candidate ligands with the target substance; and (c) a step for contacting the carrier with a solution containing the target substance and the mixture of candidate ligands obtained in step (b), and then separating and condensing a ligand, at least a part of which forms the particular conformation.