A hot-wire flow rate measuring apparatus comprises a series circuit including a first thermo-sensitive resistive element placed in the fluid path of a fluid and a first resistive element, a circuit for dividing the voltage across the first thermo-sensitive resistive element, a second thermo-sensitive resistor for temperature compensation placed in the fluid path of fluid, means for detecting the difference between the output voltage of the voltage dividing circuit and the output voltage of the second thermo-sensitive resistor for temperature compensation. Current fed to the series circuit is controlled in accordance with the detected voltage from the detecting means, and output means is provided for producing a voltage in accordance with the voltage across the resistive element, wherein the output voltage of the output means indicates a flow rate of fluid.