PURPOSE: To facilitate construction of an artificial ground by arranging a pipes in the original ground, and scattering a sand layer and a predetermined amount of foaming resin beads in the periphery of the pipee to coat those with a form thereafter, and circulating heat-generated fluid in the pipe to foam the resin beads.

CONSTITUTION: The periphery of pipes 3 is filled with sand to form a sand layer 4 after arranging the pipes 3 on the original ground 1 of a slope 2, and then unfoamed resin beads 5 are scattered on the sand, a form 6 is leaned against the slope 2. The resin beads 5 are scattered in about 2.3cm thickness by using styrene resin of about 0.9mm mean grain size for the resin beads 5. Further the pipe is covered by the form 6 of about 80cm in height and 1m2 in bottom surface. Next, foaming is performed by blowing steam of about 100°C from the pipe 3 for about 15min at a flow rate of about 0.1m3 per minute. In this way, the ground of sufficient strength further with light weight can be constructed by this foaming unit by foaming the resin beads 5 in a construction site.