Abstract: Disclosed is a flow control device for use with an intravenous set to control the flow of medicinal fluid in a barrel into patient's body. The flow control device comprises a floating member capable of being supported for floating by the buoyancy of the medicinal fluid and having a first hollowed portion facing upwards so that the hollowed portion can contain medicinal fluid and a second hollowed portion facing downwards. A linkage bar is secured to the floating member by insertion into the second hollowed portion. A membranous member is coupled via the linkage bar to the floating member such that the membranous member moves along with the floating member.