Abstract: A specimen containing a substance to be measured is introduced into a flow path of a measurement chip including a flow path which is a cavity for accommodating liquid and a reflecting unit which specularly reflects light which passes through the flow path so as to pass through the flow path again and a measurement value indicating an amount of the substance to be measured in the specimen is acquired. Then, second light acquired when first light including light of a wavelength absorbed by a red blood cell passes through the specimen in the flow path, is reflected by the reflecting unit, and passes through the specimen in the flow path again is detected in a state in which the specimen is present in the flow path. Next, a hematocrit value of the specimen is determined on the basis of a detection result of the second light. Next, a measurement value is corrected on the basis of the hematocrit value.