A method of controlling a plurality of gas sensors each including: a first measurement chamber into which an object gas is introduced, a first oxygen pump cell having a first solid electrolyte layer and paired first electrodes (17, 18) provided on the inside and outside, respectively, of the first measurement chamber, a second measurement chamber communicating with the first measurement chamber, and a second oxygen pump cell having a second solid electrolyte layer and paired second electrodes (27, 28) provided on the inside and outside, respectively, of the second measurement chamber; and a control section which executes a drive control step (S55 to S80) for adjusting an oxygen concentration of the object gas introduced into the first measurement chamber through supply of electricity to the first oxygen pump cell and for applying an ordinary voltage to the second oxygen pump cell, and a calculation step for calculating a concentration correspondence value which represents a concentration of a specific gas, on the basis of the magnitude of current flowing through the second oxygen pump cell to which the ordinary voltage is applied, the method comprising: a preliminary control step (S40 to S50, S41 to S51, S36 to S52, S37 to S50) of performing, before start of the drive control step, preliminary control which supplies a constant current to the second oxygen pump cell over a constant time, to thereby control to a constant level an amount of oxygen pumped out from the second measurement chamber to the outside of the second measurement chamber; and a read-out step of reading, out of storage means, control conditions of the sensor control apparatus which are associated with the amount of the pumped oxygen and are set for each gas sensor individually, the control conditions being determined to bring into a target range the concentration correspondence value calculated in the calculation step after start of the drive control which is started after the preliminary control is executed in a state in which a reference gas having a known concentration is introduced into the gas sensor, wherein in the preliminary control step (S40 to S50, S41 to S51, S36 to S52, S37 to S50), the preliminary control is executed under the control conditions. a first measurement chamber into which an object gas is introduced, a first oxygen pump cell having a first solid electrolyte layer and paired first electrodes (17, 18) provided on the inside and outside, respectively, of the first measurement chamber, a second measurement chamber communicating with the first measurement chamber, and a second oxygen pump cell having a second solid electrolyte layer and paired second electrodes (27, 28) provided on the inside and outside, respectively, of the second measurement chamber; and a control section which executes a drive control step (S55 to S80) for adjusting an oxygen concentration of the object gas introduced into the first measurement chamber through supply of electricity to the first oxygen pump cell and for applying an ordinary voltage to the second oxygen pump cell, and a calculation step for calculating a concentration correspondence value which represents a concentration of a specific gas, on the basis of the magnitude of current flowing through the second oxygen pump cell to which the ordinary voltage is applied, the method comprising: a preliminary control step (S40 to S50, S41 to S51, S36 to S52, S37 to S50) of performing, before start of the drive control step, preliminary control which supplies a constant current to the second oxygen pump cell over a constant time, to thereby control to a constant level an amount of oxygen pumped out from the second measurement chamber to the outside of the second measurement chamber; and a read-out step of reading, out of storage means, control conditions of the sensor control apparatus which are associated with the amount of the pumped oxygen and are set for each gas sensor individually, the control conditions being determined to bring into a target range the concentration correspondence value calculated in the calculation step after start of the drive control which is started after the preliminary control is executed in a state in which a reference gas having a known concentration is introduced into the gas sensor, wherein in the preliminary control step (S40 to S50, S41 to S51, S36 to S52, S37 to S50), the preliminary control is executed under the control conditions. a preliminary control step (S40 to S50, S41 to S51, S36 to S52, S37 to S50) of performing, before start of the drive control step, preliminary control which supplies a constant current to the second oxygen pump cell over a constant time, to thereby control to a constant level an amount of oxygen pumped out from the second measurement chamber to the outside of the second measurement chamber; and a read-out step of reading, out of storage means, control conditions of the sensor control apparatus which are associated with the amount of the pumped oxygen and are set for each gas sensor individually, the control conditions being determined to bring into a target range the concentration correspondence value calculated in the calculation step after start of the drive control which is started after the preliminary control is executed in a state in which a reference gas having a known concentration is introduced into the gas sensor, wherein in the preliminary control step (S40 to S50, S41 to S51, S36 to S52, S37 to S50), the preliminary control is executed under the control conditions.