An expiratory therapy device includes: a flow-adjusting member defining an upper chamber and a lower chamber and having an inner tube that defines an inner chamber and that is formed with wall openings a driving member an opening-controlling member including a cylindrical valve that is formed with wall apertures and that is driven by the driving member and a flow rate-enhancing member including a venturi tube that is connected to the flow-adjusting member, that has an air entrainment port, and that is provided with a jet-forming member defining a venturi orifice. The flow rate-enhancing member generates the venturi effect, such that outside air is entrained into the venturi tube through the air entrainment port and flows into the upper chamber.
