An object of the present invention is to improve inspection accuracy of a target substance detection system using Wisteria floribunda lectin. The problem is solved by 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.
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