A heater apparatus includes: a heater unit including a heater resistor; a first switching unit disposed on a downstream side of the heater resistor for on/off controlling a power supply path from a supply voltage; a second switching unit disposed on an upstream side of the heater resistor for on/off controlling the power supply path from the supply voltage; and a controller outputting first and second control signals for on/off controlling the first and second switching units, respectively. The first switching unit is switched on when the first control signal is high, and the second switching unit is switched on when the second control signal is low. The heater unit is switched on when the sensor temperature is equal to or lower than a first threshold, and is switched off when the sensor temperature is equal to or higher than a second threshold.