There is provided a polydiacetylene supramolecule comprising diacetylene molecules, capable of immobilizing a receptor molecule having a thiol group. Since the polydiacetylene supramolecule has a receptor immobilized thereon having a thiol group, for example, an antibody, and thus shows color transition when reacting with a sample, an antigen can be detected through specific color transition of the polydiacetylene when employing in a receptor-ligand reaction, for example, an antibody-antigen reaction.