To save the labor for collecting work of asphalt core.

A guide ring 12 for guiding a core bit 6 on the tip of an electric drill 1 is formed. Footrest parts 15 are integrally provided on both lateral sides of the guide ring 12. A worker puts feet F on the footrest parts 15 to fix an auxiliary tool 11, the core bit 6 is fitted to the guide ring 12 of the auxiliary tool 11 to cut a paved surface R. A core K can be straightly collected without separately using a lifting device.