[Object] A bone cement injecting tool capable of preventing the occurrence of air bubbles in the liquid as a pressure transmitting medium. [Solving Means] The bone cement injecting tool 10 is composed of a master cylinder 12, a slave cylinder 14, a first gasket 16 that slidably seals the bore of the master cylinder 12, a second gasket 18 that slidably seals the bore of the slave cylinder 14, a tube 20 for communication between the master cylinder 12 and the slave cylinder 14, water 22 filled in the space inside, a piston 24, and a pressure-retaining member 26 that applies a pressure to the forward end of said piston 24. The piston 24 moves the first gasket 16 toward the forward end, thereby delivering the water 22 to the slave cylinder 14 through the tube 20. During storage, the pressure-retaining member 26 pushes the piston 24 toward the fore-end, and this pushing force produces the pressure of the water 22.
