Target substance detection method, device, and reagent

Provided is a target substance detection method that includes: the formation of a complex in a first reaction field, by sandwiching a target substance between a first trapping substance fixed in a fixed phase and a second trapping substance labeled by a labeling substance; the separation and movement of a moiety that includes the labeling substance, from the complex to a second reaction field; and the detection of the target substance by signaling on the basis of the labeling substance in the second reaction field. As a result of this technology, a target substance in a sample can be detected with greater sensitivity and at a lower cost than when using conventional technology.