To provide a liquid force feed device in which a downward movement of a lifting bar makes an air supply ball valve element move downward by preventing the air supply ball valve element from turning in a position in which an air supply valve port is opened.

In the liquid force feed device 1, a working fluid introducing port 11, a working fluid discharge port 13, a liquid inlet port 16, and a liquid discharge port 17 are provided in a sealed vessel 2, and the opening and closing of an air supply valve 20 of the working fluid introducing port 11 and an exhaust valve 21 of a working fluid discharge port 13 are switched in response to a height of a liquid level of liquid stored in the sealed vessel 2. The ball-shaped air supply valve element 21 is disposed at the working fluid introducing port side 11 of the air supply valve port 24. The lifting bar 22 for opening the air supply ball valve element 21 is disposed penetrating through the air supply valve port 24. A conical wall member 23 for supporting the air supply ball valve element 21 in an opened state is disposed on an upper side of the air supply ball valve element 21 in an opened state. The lifting bar 22 is guided up and down by an upper part guiding member 20a and a lower part guiding member 20b.