A liquid pressure-feed device is provided wherein a working fluid discharge port can be connected to a liquid generation source side through an external pipe or can be connected to a liquid inlet port of a closed vessel without going through an external pipe. A closed vessel outer opening for opening a working fluid discharge port outwards of a closed vessel is provided and a communication passage for connecting the working fluid discharge port to a liquid inlet port is formed in the closed vessel. When connecting the working fluid discharge port to the liquid generation source side through an external pipe connected to the closed vessel outer opening, a ring member is used to provide closure between the working fluid discharge port and the liquid inlet port and provide communication between the working fluid discharge port and the closed vessel outer opening. Instead, when connecting the working fluid discharge port to the liquid inlet port, a plug member is used to close the closed vessel outer opening.