To simply construct a stable structure by stacking foam resin blocks in sequence while laying a drift preventing sheet between the foam resin blocks to construct the structure.

A drift preventing device 11 laid between foam resin blocks 3 is covered with a foam resin material 14 on the whole surface of a fiber net sheet 13, and it has stickiness to the foam resin blocks 3. The foam resin material 14 is made flat in the horizontal direction by the load applied to the drift preventing sheet 11 from above, and the contact area with the foam resin blocks 3 is increased, thus the frictional resistance between the drift preventing sheet 11 and the foam resin blocks 3 is increased. The foam resin blocks 3 are stacked in sequence while the drift preventing sheet 11 is laid between the foam resin blocks 3 to construct a structure, i.e., a road. Such a danger can be prevented that part of the structure is drifted, cracked or collapsed.