The present disclosure is to provide a measurement chip, a measuring device, and a measuring method which can accurately estimate an analyte concentration with a simple configuration. A measurement chip may include a propagation layer, an introductory part, a drawn-out part and a reaction part. Through the propagation layer, light may propagate. The introductory part may introduce the light into the propagation layer. The drawn-out part may draw the light from the propagation layer. The reaction part may have, in a surface of the propagation layer where a reactant that reacts to a substance to be detected is formed, an area where a content of the reactant changes monotonously in a perpendicular direction perpendicular to a propagating direction of the light, over a given length in the propagating direction.