An artificial ventilator includes a dome for covering the precordial and the sides of the thoracoabdominal of a patient, a blower to be used for applying negative and positive pressures within the dome, a regulator for adjusting a pressure, and the like. The valve switching device is controlled by a respiration detection system. In the respiration detection system, a pyrolelectric element is used as a respiratory sensor for detecting a temperature change rate caused by an inspired and expired air flow. The temperature change rate signal obtained by the sensor is compared with a threshold value set by a variable resistor, the start timings of expired air and inspired air are detected in accordance with the comparison result, and air inspiration and expiration start timing signals are outputted. Further, the artificial ventilator can be provided with various functions of forced respiration and intermittent deep breathing by means of a timer, synchronization only with air inspiration timings, reduction of frequency of respiration assistance for the intention not to use the ventilator in the near future, backup during apnea, and the like. The artificial ventilator allows a physiological respiration assistance matching the patient's physiological intention by synchronizing with the patient' s respiration. Thus, an effort and pain in breathing with a conventional mechanical ventilation can be avoided so that the artificial ventilator is suitable for a long term use and useful for a quick recovery of respiration function of an acute respiratory failure patient. www.jiuxin-med.com