PURPOSE: To reduce stable time of current when applying current by providing an AC voltage application means and applying AC voltage between upper and lower electrodes on measurement.

CONSTITUTION: Au is deposited on the entire surface of a glass substrate to form a lower electrode 4. Then, CuO is formed, thus forming a second thin-film member 2. In the similar manner, ZnO is formed, thus forming a first thin-film member 1. By sputtering Al, an upper electrode 3 is formed. Then, ZnO and Al are subjected to patterning to a same shape by the lift-off method using lithography for forming a combtype fine structure, thus exposing a region near an interface to the atmosphere and obtaining a junction-type chemical sensor. Then, external wirings are soldered to the upper and lower electrodes 3 and 4 and a voltage is applied to them by an AC voltage application means, thus obtaining electrical information. Since AC voltage is applied, stable time and recovery time of the junction-type chemical sensor when a voltage is applied can be reduced.