An oxygen sensor controlling apparatus includes: a controller configured to obtain a degradation index of a detection element; obtain a sensor output; detect an internal resistance of the detection element by causing a temporary change between electrodes of the detection element; successively obtain a target resistance value corresponding to the internal resistance using a first sensor output that is a value of the sensor output obtained at a time before or after a period when the temporary change occurs and the degradation index; and feedback control energization of the heater so that the internal resistance becomes the target resistance value.