PURPOSE: To allow the simple and safe exchange operation of a transfusion liquid bottle by providing a floating valve body which is formed of a material having the sp. gr. smaller than the sp. gr. of a transfusion liquid and closes the lower port of the transfusion liquid flow of a dripping cylinder when the transfusion liquid in the dripping cylinder decreases to a specified level or below in the dripping cylinder.

CONSTITUTION: The transfusion liquid 11 in a transfusion liquid part 10 drops into the dripping cylinder 1 via a dripping tube 2 if this liquid exists above the inflow port of a bottle needle 12. The floating valve body 6 floats to open the transfusion liquid downflow port and the dripping is executed in the state in which the transfusion liquid 11 in the dripping cylinder 1 accumulate buoyancy above the level above at which the transfusion liquid 11 in the dripping cylinder 1 floats the floating valve body 6. The transfusion liquid 11 in the dripping cylinder 1 decreases and the floating valve body 6 descends as well when there is no more transfusion liquid 11 in the transfusion liquid bottle 10 and there is no more dropping into the dripping cylinder 1. The floating valve body 6 seats to close the transfusion liquid downflow port when the transfusion liquid 11 in the dripping cylinder 1 decreases down to the level at which there is no more buoyancy to float the floating valve body 6. The transfusion liquid is kept filled in a downflow tube 4 in this way. There is no infiltration of the air into the downflow tube 4 even if the dripping is interrupted in the state in which the transfusion liquid 11 remains slightly in the dripping cylinder 1 and even if the transfusion liquid bottle 10 is removed.