The present invention relates to a gas concentration measuring device. The present invention relates to a gas concentration measuring method using a gas concentration measuring device, and the gas concentration measuring device comprises: an exhalation path through which exhalation flows； a sample gas chamber which is in communication with the exhalation path and into which a sample gas which is a part of the exhalation flowing in the exhalation path is introduced； a semiconductor gas sensor which is arranged in the sample gas chamber and which comprises a sensor for generating an electrical signal according to the concentration of the gas being measured and a heater for heating the sensor； and a controller which controls the heater and receives the electrical signal from the semiconductor gas sensor to calculate the concentration of the gas being measured. The gas concentration measuring method comprises: a) a warming-up step for heating the sensor by applying electric power to the heater； b) a stabilization determination step for measuring a resistance value of the sensor in a state in which a measurement step heater power (Pm) is applied to the heater； c) a step for introducing exhalation into the exhalation path； d) a measurement standby step for applying the measurement step heater power (Pm) to the heater； and e) a step for calculating the concentration of the gas being measured by receiving the electrical signal from the semiconductor gas sensor, when the exhalation is introduced into the exhalation path, wherein if it is determined that the sensor is stable in step b), then step e) is performed after step b), and if it is determined that the sensor is unstable in step b), then step c), step d), and step e) are sequentially performed after step b).La présente invention concerne un dispositif de mesure de concentration de gaz. La présente invention concerne également un procédé de mesure de concentration de gaz faisant appel à un dispositif de mesure de concen
