A rod body (30) is formed of magnetostrictive material and includes one end portion (30a) fixed, and a piston (35) is fixed to the other end portion (30b) of the rod body (30). The piston (35) is slidably disposed within a cylinder (36) in which there is formed a pump chamber (37). A suction port (39) for sucking lubricating oil into the pump chamber (37) is formed in the cylinder (36), while a suction valve (40) for preventing the lubricating oil from flowing out from the suction port (39) is disposed in the suction port (39). In the cylinder (36), there is disposed a nozzle (20) which communicates with the pump chamber (37) and has a sectional area smaller than the lubricating oil passage sectional area of the suction valve (40). There is disposed a coil (43) outside the rod body (30) and, to the coil (43), there is connected a control device (6) for controlling the supply of a current to be supplied to the coil (43).