Disclosed is a device for controlling an interface of a liquid-liquid extraction column using pressure equilibrium. The device includes a vertical pipe provided beside an extraction column parallel thereto. The device enables internal pressures of the extraction column and the vertical pipe to be balanced with each other by moving fluid from the extraction column into the vertical pipe. Therefore, the device can maintain the level of an interface between fluids having different specific gravities with a simple control system. The device includes the liquid-liquid extraction column having a column body; and upper and lower tanks having respective inlet pipes and respective outlet pipes, wherein a pipeline is connected to the outlet pipe of the lower tank, and the internal pressures are balanced by controlling a level of the fluid in the pipeline, thereby maintaining the level of the interface.