PURPOSE: To correct the characteristic of a humidity detecting element, the electric resistance of which changes when the humidity changes, that the resistance value of the element changes in accordance with the temperature.

CONSTITUTION: This instrument uses a humidity detecting element 1 and temperature defecting element 2 having a characteristic equivalent to the temperature characteristic of the element 1 and a control circuit 4 which selectively drives the elements 1 and 2 by means of an R-f conversion circuit 3. The instrument also uses a control circuit which selectively drives a resistance element having no temperature-depending characteristic. Since it is unnecessary to newly add any element for correcting temperature, the temperature of the instrument can be corrected with a simple constitution and the size and cost of the instrument can be reduced.