Provided is a method for measuring the concentration of a substance in a blood sample, the method comprising the steps of: supplying the blood sample to a biosensor comprising a hematocrit electrode for measuring a hematocrit value on the surface of which electrode an electrically conductive polymer is coated by physical adsorption in the absence of a crosslinking agent; and calculating the concentration of the substance from the measured value of a first current resulting from application of a first voltage; and correcting the concentration of the substance with the value of a second current resulting from application of a second voltage or the hematocrit value calculated from the value of the second current.