The present invention provides an immunochromatography detection method capable of suppressing non-specific reactions. The present invention relates to an immunochromatography detection method including: a step of adding an analyte dilution solution containing an analyte to a chromatography medium; a step of recognizing a detection target by a labeling substance modified with gold nanoparticles, which is dry-retained at a labeling substance retaining part; a step of developing a composite of the labeling substance and the detection target as a mobile phase; and a step of detecting the detection target in the developed mobile phase at a judgment part, wherein the labeling substance is protected with a polyalkylene glycol having one or more mercapto groups and/or a derivative thereof and then dry-retained together with arginine and casein at the labeling substance retaining part.