To provide a base course material of high quality such that a base course will not weaken when the surface temperature of the base course rises in the summer, since asphalt contained in waste asphalt concrete can be completely removed.

Collected waste asphalt concrete 1 is crushed, and as the concrete 1 is agitated while waste asphalt is melted by heating, it is mixed sufficiently with sawdust 5 added thereto. Then, after the sawdust 5 is carburized by temperature elevation, natural cooling is effected. The mixture is classified into grain sizes of less than 3 mm and those of 3 mm or more for use as protective sand 7 or base course material 8 during the burial of pipe. Plant residue, such as rice husks, rice bran, defatted sesame, or been curd lees, may be used in place of the sawdust 5.