A control apparatus (100) for a gas sensor (10) which includes a cell (2) composed of a solid electrolyte body and a pair of electrodes provided thereon. The control apparatus includes voltage application means (70) for applying a single pulse voltage to the cell over a constant energization time T; first-output-value obtaining means 70 for obtaining a first output value Vri1 from the cell when a first time t1 shorter than the constant energization time has elapsed; second-output-value obtaining means (70) for obtaining a second output value Vri2 from the cell when a second time t2 shorter than the constant energization time but longer than the first time has elapsed; and deterioration-degree detection means 70 for detecting the degree of deterioration of the cell on the basis of a difference ΔVri between the second output value and the first output value.