Provided are a method of forming a signal probe-polymer which makes it possible to form a polymer efficiently and quantitatively, a signal probe-polymer formed by the method, oligonucleotide probes for use in the method, and a method of detecting target analyte having high sensitivity and excellent quantitative capability. The method of forming a signal probe-polymer comprises reacting a plurality of pairs of oligonucleotide probes with each other to form a polymer, a first probe of the pair of oligonucleotide probes comprising three nucleic acid regions of X, Y, and Z regions, located in the stated order from the 5′-terminal and a second probe comprising three nucleic acid regions of X′, Y′, and Z′ regions, located in the stated order from the 5′-terminal, wherein each region of the oligonucleotide probes has a length of from 13 to 15 bases.