PURPOSE: To provide complete support of a guard rail without the sacrifice of the soundness of a road body by fixing its lower end on floor system concrete, inserting a supporting pole into the cylindrical body expanded to the surface of a bed, and charging and fixing an asphalt material.

CONSTITUTION: When floor system concrete 5 is placed on a road body 1 where plural road body factors 3 made of foam styrene are laid, a concrete hume piping 17 with the axial length reaching the surface of a bed is arranged for fixture to place concrete 5. Next a bed 7 is constructed to apply paving asphalt 9, and a supporting pole 15 fixing a guard rail 13 is inserted in the hume piping 17 and under that condition, an asphalt material 23 is charged to fix the supporting pole 15. This provides a guard rail supporting structure suitable for the road body 1 consisting of extra-light material, ease of work, a short period of work and reduced manpower.