To provide a catch tank device for an air dryer device which although simply and inexpensively configured, hardly discharge carelessly for example, moisture, oil and dust, and thus less effects environment, while maintaining desired purging performance with a small airflow resistance.

The catch tank device 100 for the air dryer device separates the water from a purged air that is discharged in purging processing of the air dryer device 10 and stores the water. The device includes: an air moisture separating passage 130 that introduces the purged air that is discharged in the purging processing of the air dryer device 10, makes the introduced purged air collide with an inner wall of a cylindrical element which is bended several times to separate the air and the moisture; and a catch tank 110 that introduces the moisture separated from the purged air in the air moisture separating passage 130 via a discharge port 133 provided near the bottom part of the air moisture separating passage 130 and stores the moisture.