Disclosed is a method for detecting a target substance, comprising: forming on a carrier a complex comprising Wisteria floribunda lectin (WFA) and a target substance by mixing the WFA immobilized on the carrier with the target substance comprising a sugar chain that binds to the WFA in the presence of an alcohol having 1 to 7 carbon atoms consisting of carbon atoms, hydrogen atoms, and oxygen atoms; and detecting the target substance by detecting the complex.