PURPOSE: To control tube pressure in such a way as preventing the rise thereof by causing a controller to control a pump drive motor via a converter, according to the tube pressure detected with a pressure sensor, and providing a branch pipe having a leak valve between a pump and a nozzle for causing a necessary amount of a high viscosity fluid to leak.

CONSTITUTION: A lubricant 12 in a tank 11 is sent to a feed line 14 via a pump 13. This feed line 14 is opened and closed with a valve 16. Pressure in the line 14 is detected with a sensor 17 and the signal thereof is transmitted to a controller. This controller controls a pump drive motor 18 through a converter, according to the pressure detected with the sensor 17. As a result, tube pressure can be maintained at constant level without any need to use a safety valve. Also, desired tube pressure can be easily obtained via the adjustment of a leak amount, when a leak valve is fitted for causing a fluid to leak. In this case, the leak valve can be made to act as a safety valve, as well.