To provide at low-cost a small and light oil supply device for a pneumatic operating machine using a high pressure air as a working fluid, with which it is possible to use a lubricant oil to be sent to moving parts such as piston, rotor, or the like even in case the construction is light and small and the air pressure working is high.

A high pressure air duct 4 is branched on the way of an air duct 3 for a high pressure air to actuate an air hammer device 1, and an oil pressure booster 6 is furnished to work with the high pressure air fed through the air dust, and the primary side oil supply port 6l of the oil pressure booster 6 is connected with a tank 7 for lubricant oil. The secondary side oil discharge port 6m with high pressure of the oil booster 6 is connected with the air duct 3 in a position upstream of the air duct 4, and the rate of boosting of the booster 6 is set so that the oil pressure of lubricant at the secondary port 6m is equal to or some higher than the air pressure in the air duct 3.