To reduce a cost of a lubricating oil tank by eliminating necessity for forming the lubricating oil tank to resist against a high pressure.

In this halfways of an air pipe line 1 supplying lubricating oil L with compressed air A to the inside of a drilling machine, an oil feed nozzle 2 is provided, and to this oil feed nozzle 2, an lubricating oil path 6 is connected, which supplies the lubricating oil L from an lubricating oil tank 3 through a lubricating oil pump 4 and a flow regulating valve 5 with temperature/pressure compensation. When an operating oil tank of a hole drilling device is used as the lubricating oil tank 3, necessity for providing a separate lubricating oil tank is eliminated, and when an oil hydraulic pump for driving a hydraulic equipment of the hole drilling device is used as the lubricating oil pump 4, necessity for providing a separate lubricating oil pump is eliminated.