To provide a means for preventing degradation in bore positioning accuracy due to run-out of a drill and breakage of the drill, preventing wrapping of debris and chips around a drill bit even when the drilling frequency is increased with the same drill in small-bore diameter drilling using an entry board with a lubricating layer.

The lubricating layer 4 formed on at least one surface of an aluminum-made board 2 is composed of mixed composition containing polyethylene glycol having a number average molecular weight equal to or higher than 100 and under 1000, polyethylene glycol having a number average molecular weight equal to or higher than 10000, chelating agent and trimethylol propane.