The CPAP device which is small in size and can improve the detection accuracy of a sensor is provided. A fan unit 17 produces an airflow. A pressure difference generating member 32 causes a pressure difference in the airflow. A sensor detects a pressure difference between the air pressure on the upstream side of the pressure difference generating member 32 and the air pressure on the downstream side thereof. A straightening plate 31 is provided between the fan unit 17 and the pressure difference generating member 32, and straightens the airflow produced by the fan unit 17. A straightening plate 31 comprises a first fin 31b and a second fin 31c which are arranged along the airflow, and a lattice-like third fin 31d which is arranged on the downstream side of the first fin 31b and the second fin 31c, and through which the airflow through the first fin 31b and the second fin 31c passes.
