A contactless temperature-measuring device especially for a respiration humidifier with a flow channel for breathing gas, which is improved in respect to handling and reliability of measurement. The device includes: a hollow body (1), which is closed towards the flow channel (2, 6), extends into the flow channel (2, 6) for assuming the temperature in the flow channel (2, 6); and an infrared detector (3, 7) is directed toward the inner surface of the hollow body (1) extending into the flow channel (2, 6) for the contactless detection of the temperature of the hollow body (1).