A method for measuring pressure of a gaseous fuel compressed in a feed system of an engine equipping a motor vehicle, by a pressure measuring device having an infrared quality sensor and an electronic control unit, the measuring method being characterized in that it consists in determining a corrected absorbance value of the fuel based on absorbance measurements performed by infrared analysis, at preset wavelengths, and in comparing the value to a nominal absorbance value, determined beforehand based on absorbance measurements performed at a nominal pressure after a pressure stabilization phase of the fuel and at the same said wavelengths, in order to determine the fuel pressure.