PURPOSE: To prevent the occurrence of temperature rise at a bearing and avoid lube fouling of a work by connecting a vacuum pump to an exhaust port for lube suction and draining lube from a drainage pipe connected to the vacuum pump.

CONSTITUTION: A vacuum pump 6 has one side connected to an exhaust port 5 and the other side connected to a drainage pipe 7. The vacuum pump 6 is connected to a vent pipe 6a, from which compressed air is supplied and readily exhausted to the exhaust pipe 7 to make the vacuum pump into a vacuum. Lube is supplied into an oil passage 4 together with compressed air and drained from the exhaust port 5 after passing through a bearing 3 for lubrication. As the vacuum pump 6 is connected to the exhaust port 5, lube is forcibly sucked together with compressed air to smooth the drainage of tube from the exhaust port 5. In addition, as the vacuum pump 6 is connected to the drainage pipe 7, lube is drained and collected.