To restrict pressure fluctuation by pulsation specific to a pump, enable to maintain processing precision on demand without applying a postprocess by man's hand or a machine while extremely restricting energy loss, and almost completely prevent heat generation in a table.

This device is composed of factory air 39 as a pressure control means to control pressure in a static pressure gap by controlling flow of static pressure oil to be supplied to the static pressure gap, a first air pressure generated by the factory air 39, a booster 40 to boost the first air pressure, a second air pressure generated by the booster 40, a reservoir tank 41 to store the second air pressure, a pressure reducing valve 44 provided with a relief function to reduce the second air pressure outgoing from the reservoir tank 41, and a pressurizing tank 32 to store static pressure oil to which a third air pressure generated from the pressure reducing valve 44 provided with the relief function is applied.