Two novel biosensors, non-labeling and labeling immunosensors, have been developed by unique combination of solid-phase (membrane-bound) antibody with electrochemical sensing devices. Both immunosensors showed excellent selectivity due to immunochemical specific affinity of membrane-bound antibody to the corresponding antigen. A non-labeling immunosensor was designed for the determination of antigen by measuring transmembrane potential across an antibody-bound membrane. A labeling immunosensor was facilitated with chemical amplification of labeling enzyme along with an antibody-bound membrane. Calibration curves were obtained for human serum albumin in the range 10-5–10-3 g/ml and 10-8–10-5 g/ml with the non-labeling and labeling immunosensors, respectively. Practical importance of chemical amplification is discussed in relation to biomedical sensing systems.