Abstract: A compressed air dehumidifying device, comprising: an external cylinder having an inlet port for the compressed air fed from the compressor, a passageway and an outlet port for the clean compressed air dehumidified and purged of oil, dirt, and dust, and a drain hole for discharging the moisture, oil, dirt, and dust out of the device; and an internal cylinder having a passageway connected to the inlet port for compressed air, orifices for explosively injecting the compressed air that are connected to the passageway, and inverted-funnel-shaped injection tubes adjoining the respective orifices and the diameter of which is gradually increased along the axis, and being formed in the external cylinder.