A microdevice for the measurement of the respiratory activity of cells was fabricated using a microfabricated Clark-type oxygen electrode. The oxygen electrode was completed in a dry state and was activated by introducing water necessary for the reduction of oxygen in the form of water vapor through an oxygen-permeable membrane, which significantly facilitated handling of the device even by nonspecialists. The use of a thin paper layer stabilized the current response and enabled stable continuous operation of the oxygen electrode without current disturbance caused by the evaporation of water. The microdevice was tested in some model experiments including the measurement of the respiratory activity of Escherichia coli (E. coli), evaluation of the efficacy of antibiotics, and measurement of the antibacterial activity of neutrophils, all of which demonstrated that the consumption of dissolved oxygen by cells can be monitored clearly by following an easy procedure for the preparation of the measurements.