A method of controlling a gas sensor to suppress deterioration of accuracy caused due to temperature change, said gas sensor comprising a plurality of cells (110, 120, 130) which each comprise a solid electrolyte layer (111, 121, 131) and a pair of electrodes (112, 13, 122, 123, 132, 133) disposed on said solid electrolyte layer, and a heater adapted for heating at least one of said cells, said gas sensor being adapted for outputting a concentration signal corresponding to a concentration of a specific gas component present in a gas to be measured via one of said cells, said gas sensor being adapted for connecting to a gas sensor control apparatus which is connected with an external device, said method comprising: an internal resistance detection step of detecting a value of an internal resistance of one of said cells as an objective cell; a concentration value detection step of detecting with a concentration detection means a value of the concentration of said specific gas component on the basis of said concentration signal and outputting the value of the concentration to said external device; a heater current supply control step (S6, S9) of controlling a current to be supplied to said heater such that the value of the internal resistance detected in said internal resistance detection step becomes a target value; a determination step of determining whether there is deterioration in accuracy in concentration detection by the concentration detection means, which is caused due to temperature change of said gas sensor, by determining whether or not the value of the internal resistance detected in said internal resistance detection step is within a permissible range including said target value and whose upper limit is less than an internal resistance value for determining whether to start driving of said cells; a nullification information generation step (S10, S18) of generating nullification information to nullify the value of the concentration which is detected in said concentration value detection step when it is determined in said determination step that the value of the internal resistance detected in said internal resistance step is out of said permissible range; and a nullification information output step (S10, S18) of outputting said nullification information to said external device. an internal resistance detection step of detecting a value of an internal resistance of one of said cells as an objective cell; a concentration value detection step of detecting with a concentration detection means a value of the concentration of said specific gas component on the basis of said concentration signal and outputting the value of the concentration to said external device; a heater current supply control step (S6, S9) of controlling a current to be supplied to said heater such that the value of the internal resistance detected in said internal resistance detection step becomes a target value; a determination step of determining whether there is deterioration in accuracy in concentration detection by the concentration detection means, which is caused due to temperature change of said gas sensor, by determining whether or not the value of the internal resistance detected in said internal resistance detection step is within a permissible range including said target value and whose upper limit is less than an internal resistance value for determining whether to start driving of said cells; a nullification information generation step (S10, S18) of generating nullification information to nullify the value of the concentration which is detected in said concentration value detection step when it is determined in said determination step that the value of the internal resistance detected in said internal resistance step is out of said permissible range; and a nullification information output step (S10, S18) of outputting said nullification information to said external device.