An object of the present invention is to provide a kit, a method, and a reagent which prevent the problem of false positive due to nonspecific adsorption, suppress the increase in noise to be generated, and are capable of achieving high-precision measurement of a measurement target substance in a wide concentration range from a low concentration to a high concentration. According to the present invention, there is provided a kit for measuring a measurement target substance, the kit including: a first particle having a label and modified with a first binding substance; a second particle having no label and modified with a second binding substance; a flow channel for flowing the first particle and the second particle; and a substrate having a third binding substance capable of specifically binding to the measurement target substance or a substance capable of binding to the first binding substance, in which the first particle having a label is a luminescent labeled particle containing at least one kind of compound represented by Formula (1) and a particle. Each symbol in Formula (1) has the meaning described in the present specification.