A biosensor system, comprising: a measuring instrument having an operation part having a CPU, and a sensor chip that is insertable into and removable from the measuring instrument and into which a blood sample is to be introduced, wherein the sensor chip includes a measurement part A including a working electrode and a counter electrode for acquiring Data a related to a concentration of an analyte in a blood sample based on the amount of electric current that flows in the blood sample due to a reaction in which an oxidoreductase with the analyte used as a substrate is involved, a measurement part B including a counter electrode and a working electrode for acquiring Data b based on the amount of electric current that flows in the blood sample according to oxidation or reduction of a redox substance other than the analyte, and a reaction reagent layer containing the oxidoreductase formed on the working and counter electrodes (12, 13) of the measurement part A and the counter electrode of the measurement part B but not on the working electrode of the measurement part B, wherein the CPU is adapted to - apply voltage to the electrodes of the measurement parts A and B (41, 42), - acquire Data a and Data b as electric current values from the measurement parts A and B (41, 42) following the voltage application, and - determine the concentration of the analyte in the blood sample to be evaluated based on the Data a and the Data b; characterized in that the operation part has a conversion table in which Data c, Data d, and the concentration of the analyte in a reference blood sample corresponding to the Data c and the Data d are described, where the Data c is related to the amount of electric current that flows in the reference blood sample due to a reaction in which the oxidoreductase with the analyte used as a substrate is involved and the Data d is related to the amount of electric current that flows in the reference blood sample according to oxidation or reduction of a redox substance other than the analyte; and the CPU is adapted to determine the concentration of the analyte in the blood sample based on the Data a and the Data b with referring to the conversion table. a measuring instrument having an operation part having a CPU, and a sensor chip that is insertable into and removable from the measuring instrument and into which a blood sample is to be introduced, wherein the sensor chip includes a measurement part A including a working electrode and a counter electrode for acquiring Data a related to a concentration of an analyte in a blood sample based on the amount of electric current that flows in the blood sample due to a reaction in which an oxidoreductase with the analyte used as a substrate is involved, a measurement part B including a counter electrode and a working electrode for acquiring Data b based on the amount of electric current that flows in the blood sample according to oxidation or reduction of a redox substance other than the analyte, and a reaction reagent layer containing the oxidoreductase formed on the working and counter electrodes (12, 13) of the measurement part A and the counter electrode of the measurement part B but not on the working electrode of the measurement part B, a measurement part A including a working electrode and a counter electrode for acquiring Data a related to a concentration of an analyte in a blood sample based on the amount of electric current that flows in the blood sample due to a reaction in which an oxidoreductase with the analyte used as a substrate is involved, a measurement part B including a counter electrode and a working electrode for acquiring Data b based on the amount of electric current that flows in the blood sample according to oxidation or reduction of a redox substance other than the analyte, and a reaction reagent layer containing the oxidoreductase formed on the working and counter electrodes (12, 13) of the measurement part A and the counter electrode of the measurement part B but not on the working electrode of the measurement part B, wherein the CPU is adapted to - apply voltage to the electrodes of the measurement parts A and B (41, 42), - acquire Data a and Data b as electric current values from the measurement parts A and B (41, 42) following the voltage application, and - determine the concentration of the analyte in the blood sample to be evaluated based on the Data a and the Data b; - apply voltage to the electrodes of the measurement parts A and B (41, 42), - acquire Data a and Data b as electric current values from the measurement parts A and B (41, 42) following the voltage application, and - determine the concentration of the analyte in the blood sample to be evaluated based on the Data a and the Data b; characterized in that the operation part has a conversion table in which Data c, Data d, and the concentration of the analyte in a reference blood sample corresponding to the Data c and the Data d are described, where the Data c is related to the amount of electric current that flows in the reference blood sample due to a reaction in which the oxidoreductase with the analyte used as a substrate is involved and the Data d is related to the amount of electric current that flows in the reference blood sample according to oxidation or reduction of a redox substance other than the analyte; and the CPU is adapted to determine the concentration of the analyte in the blood sample based on the Data a and the Data b with referring to the conversion table.