PROBLEM TO BE SOLVED: To provide a breathing gas heating humidifier with a higher humidification efficiency of a breathing gas, the heating humidifier being capable of operating continuously with a humidification capability kept stably even when supplying the breathing gas at high flow rate.SOLUTION: A chamber 3 of a water breathing gas heating humidifier 100 includes an inlet 41 for taking in a breathing gas in the chamber 3, an outlet 51 for guiding the breathing gas humidified in the chamber 3 to the outside, a water supply port 61 for supplying water in the chamber 3, a heating plate 81 disposed vertically and to be heated by the heater 22, and a first sheet-like humidification member 11A soaked in the water in the chamber 3 to be kept in humid condition. The first sheet-like humidification member 11A is disposed so as to come in surface contact with the heating plate 81 and to allow the breathing gas to circulate along a surface of the heating plate. The water supply port 61 is disposed so as to supply the water toward an upper part of the heating plate 81.SELECTED DRAWING: Figure 3
