This sensor chip (11) comprises a substrate (15) in the form of a flat board, a sample inlet (20) that is provided in the thickness direction of the substrate (15) and into which flows the blood (3) used for measurement, a supply path (21) that communicates with this sample inlet (20), and detection electrodes (17, 18, 19) provided to this supply path (21), wherein the substrate (15) is provided with a surplus blood reservoir (25) that draws in surplus blood (3a) and holds this drawn surplus blood (3a).