An object of the invention is to realize a thermal gas flow sensor capable of reducing time fluctuation of a heating resistor. A heating resistor 3 and thermometric resistors 4 and 14 are formed on a surface of a thin-wall portion 2. Electrode drawn wires 18 to 23 and pad portions 8 to 13 are formed so as to draw signal lines from the heating resistor 3 and the thermometric resistors 4 and 14. Contact portions 24 to 29 are formed to come in contact with the heating resistor 3, the thermometric resistors 4 and 14, and the electrode drawn wires 18 to 23. The heating resistor 3 and the thermometric resistors 4 and 14 are covered with protective films 30a, 30b, and 31a and insulating films 31b and 30c. The protective films 31a and 31b are formed of a dense film formed of nitride or the like. A part coming in contact with a drawn wire portion 34 and the heating resistor 3 is covered with a contact barrier metal film 36 (titanium-based electrical conductor such as titanium nitride, titanium tungsten, and titanium). The titanium-based electrical conductor is a dense film and resistant to hydrogen. Therefore, it is possible to reduce a time fluctuation of the heating resistor.