A moisture-permeable and water-resistant film 6 that is disposed around the inner circumference of the tubular outer shell 2 and the outer shell 2, forms a water retention region 10 between the outer shell 2, and forms a ventilation region 12 on the inner surface side thereof； A water supply port 14 provided in the outer shell 4 for supplying water to the water retention region 10 and the outer side of the outer shell 4 are arranged to heat the water in the water retention region 10 to generate water vapor, and to generate water vapor. And a heater 8 for heating the intake gas flowing through the water, the water supplied from the water supply port 14 is held in the water retention region 10 by the moisture permeable and water resistant film 6, and only the water vapor generated by the heating of the heater 8 is permeable. An artificial airway 2 that passes through the moisture-resistant film 6 and flows into the ventilation region 12 to heat and humidify the intake gas flowing in the ventilation region 12 and a breathing circuit including the artificial airway 2 are provided.チューブ状の外殻２と、外殻２の内面全周に配設され、外郭２との間に保水領域１０を形成し、その内面側に通気領域１２を形成する透湿耐水膜６と、保水領域１０に水を供給するため外郭４に設けられた給水口１４と、外殻４の外側に配接され、保水領域１０内の水を加熱して水蒸気を発生させるとともに、通気領域１２内を流れる吸気ガスを加温するヒータ８と、を備え、給水口１４から供給された水が、透湿耐水膜６により保水領域１０内に保持され、ヒータ８の加熱により生じた水蒸気だけが透湿耐水膜６を通過して通気領域１２内に流入して、通気領域１２内を流れる吸気ガスを加温及び加湿する人工気道２及び人工気道２を備えた呼吸回路を提供する。
