A deterioration signal generation device for a gas sensor for simulating a deterioration signal (Vout) output by a gas sensor in a deteriorated state, the gas sensor being arranged to detect the fuel-air ratio of exhaust gas from an internal combustion engine based on the concentration of particular components in the exhaust gas, the deterioration signal generation device comprising: a reference signal acquisition unit (11, 101) which is connected to a reference sensor identical in configuration to the gas sensor for outputting a reference signal (Vin) for generating the deterioration signal (Vout), the reference signal being associated with the concentration of the particular component in the exhaust gas, and which is arranged to acquire the reference signal (Vin) at constant time intervals; a reference signal storing unit adapted to store the reference signals (Vin) acquired by the reference signal acquisition unit in the order of acquisition; an input unit adapted to allow a user to input set values; a delay time setting unit (11, 104) adapted to set a delay time for outputting the reference signal (Vin) by delaying the starting point of a change in the signal as a result of a change in a target fuel-air ratio of a mixture supplied to the internal combustion engine; and a signal delay generation unit (11, 104) adapted to generate the reference signal (Vin) stored in the reference signal storing unit (11, 104) at a time preceding the current opportunity for acquisition by a number of times corresponding to the delay time set by the delay time setting unit (11, 104) as deterioration signal (Vout); wherein the deterioration signal generation device is adapted to output the generated reference signal (Vin) as the deterioration signal (Vout) to an electronic control unit. a reference signal acquisition unit (11, 101) which is connected to a reference sensor identical in configuration to the gas sensor for outputting a reference signal (Vin) for generating the deterioration signal (Vout), the reference signal being associated with the concentration of the particular component in the exhaust gas, and which is arranged to acquire the reference signal (Vin) at constant time intervals; a reference signal storing unit adapted to store the reference signals (Vin) acquired by the reference signal acquisition unit in the order of acquisition; an input unit adapted to allow a user to input set values; a delay time setting unit (11, 104) adapted to set a delay time for outputting the reference signal (Vin) by delaying the starting point of a change in the signal as a result of a change in a target fuel-air ratio of a mixture supplied to the internal combustion engine; and a signal delay generation unit (11, 104) adapted to generate the reference signal (Vin) stored in the reference signal storing unit (11, 104) at a time preceding the current opportunity for acquisition by a number of times corresponding to the delay time set by the delay time setting unit (11, 104) as deterioration signal (Vout); wherein the deterioration signal generation device is adapted to output the generated reference signal (Vin) as the deterioration signal (Vout) to an electronic control unit.