The present invention addresses the problem of providing a kit, a method and a reagent capable of accurately measuring a measurement target substance across a broad concentration range extending fromlow to high concentrations, suppressing an increase in produced noise, and preventing against the problem of false positives caused by nonspecific adsorption. The present invention provides a kit which measures a measurement target substance and includes first particles which have a marker and are modified with a first binding substance, second particles which do not have a marker and are modifiedwith a second binding substance, a channel through which the first and second particles flow, and a substrate which has either a third binding substance which specifically binds to the measurement target substance or a substance which binds to the first binding substance, wherein the first particles which have the marker are light-emitting marker particles containing particles and at least one type of compound represented by formula (1). The symbols in formula (1) are as described in the description of the present application.