To shorten a response time by enabling proper driving control to be performed according to a load state.

This pump is provided with a pump part 7 for discharging fluids by the reciprocating movement of a piston 5 housed in a housing 3, and a piston driving part 11 having an ultramagnetostrictive element 9 Extended when a magnetic field is applied and a coil 22 for applying a magnetic field to the ultramagnetostrictive element by current application and adapted to reciprocate the piston 5. In this case, a current frequency setting means for changing the frequency of a current applied to the coil 22 is provided in a controller 33, and setting is changed from a high applied current frequency to a low frequency corresponding to a specified time or a discharge route output pressure.