A gas sensor comprising: a first thermistor (Rd1) having a resistance value that changes according to a concentration of a first gas with a first sensitivity and changes according to a concentration of a second gas with a second sensitivity; a second thermistor (Rd2) connected in series to the first thermistor (Rd1), the second thermistor (Rd2) having a resistance value that changes according to a concentration of the first gas with a third sensitivity that is lower than the first sensitivity and changes according to a concentration of the second gas with a fourth sensitivity that is different from the second sensitivity; a correction resistor (R1) connected in parallel with the first (Rd1) or second (Rd2) thermistor, wherein a resistance value of the correction resistor (R1) is selected based on a ratio of the second sensitivity and the fourth sensitivity so as to cancel a change in potential at a connection point between the first (Rd1) and second (Rd2) thermistors according to the concentration of the second gas; a first heater (MH1) configured to heat the first thermistor (Rd1) to a first temperature based on a first control voltage (Vmh1); a second heater (MH2) configured to heat the second thermistor (Rd2) to a second temperature different from the first temperature based on a second control voltage (Vmh2); a first amplifier configured to receive a common control voltage (Vmh) and apply the first control voltage (Vmh1) to the first heater (MH1); and a second amplifier configured to receive the common control voltage (Vmh) and apply the second control voltage (Vmh2) to the second heater (MH2), wherein a gain of the first amplifier and a gain of the second amplifier are different from each other. a first thermistor (Rd1) having a resistance value that changes according to a concentration of a first gas with a first sensitivity and changes according to a concentration of a second gas with a second sensitivity; a second thermistor (Rd2) connected in series to the first thermistor (Rd1), the second thermistor (Rd2) having a resistance value that changes according to a concentration of the first gas with a third sensitivity that is lower than the first sensitivity and changes according to a concentration of the second gas with a fourth sensitivity that is different from the second sensitivity; a correction resistor (R1) connected in parallel with the first (Rd1) or second (Rd2) thermistor, wherein a resistance value of the correction resistor (R1) is selected based on a ratio of the second sensitivity and the fourth sensitivity so as to cancel a change in potential at a connection point between the first (Rd1) and second (Rd2) thermistors according to the concentration of the second gas; a first heater (MH1) configured to heat the first thermistor (Rd1) to a first temperature based on a first control voltage (Vmh1); a second heater (MH2) configured to heat the second thermistor (Rd2) to a second temperature different from the first temperature based on a second control voltage (Vmh2); a first amplifier configured to receive a common control voltage (Vmh) and apply the first control voltage (Vmh1) to the first heater (MH1); and a second amplifier configured to receive the common control voltage (Vmh) and apply the second control voltage (Vmh2) to the second heater (MH2), wherein a gain of the first amplifier and a gain of the second amplifier are different from each other. <EOS>