To provide the heater trouble detector of a gas sensor capable of returning the gas sensor to a normal state, when the heater trouble of the gas sensor is temporarily detected.

The heater trouble detector of the gas sensor is equipped with the current restriction means 7, provided to a heater current supply means 1 to restrict a heater current to a preset restricted current value; a control means 4 constituted so as to compare the heater current, detected by a current detection means Rd, 3 with a heater current value at normal time and operating the current restriction means 7 in a case that the heater current becomes an abnormal value or higher than the current value at the time of normality and a release means 4, for comparing the heater current detected by the current detection means Rd, 3 after the current restriction means 7 has been operated with a normal current determine value preset so as to be made lower than the restricted current value and releasing the operation of the current restriction means 7, when the heater current becomes a normal determination value.

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