An amperometric biosensor is adapted for detecting concentration of a target analyte, and includes a detector and a plurality of sensing members connected electrically to form an input of the detector. Each sensing member includes an electrode unit including a working electrode with a biorecognition element disposed thereon for reaction with the target analyte, and a reference electrode. Each sensing member receives the target analyte, so as to bring the target analyte into contact with the working and reference electrodes. The detector provides a voltage to each electrode unit, so as to generate a current that flows through the target analyte and that is detected for subsequent concentration analysis of the target analyte.