Abstract: Provided is a target substance detection method that includes: forming a complex in a first reaction field, by sandwiching a target substance between a first trapping substance immobilized on a solid phase and a second trapping substance labeled with a labeling substance; separating a moiety that includes the labeling substance from the complex; moving the moiety to a second reaction field; and detecting the target substance by a signal based on 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.