To provide a structure for preventing the adhesion of a metal piece, which prevents the metal piece of a vehicle from adhering to a joint section between guardrails even if the vehicle such as an automobile is brought into contact with the guardrail at an acute angle.

In this structure 1 for preventing the adhesion of the metal piece, a sliding part 4 is formed near the joint section 3 at least in an overhanging area 5a and near a fixing bolt 6 for the joint section 3 on the guardrail 2 which is constituted by making corrugated plate-like beams 5 overlap each other from the overhanging area 5a and a sunken area 5b so as to elongate them. When the vehicle such as the automobile comes into contact with the guardrail 2, the sliding part 4 makes a fender of the vehicle and the edge of a door slide on the sliding part 4, and makes the fender and the edge of the door go over a step of the end 5c of one plate-like beam 5 in the joint section 3 between the guardrails 2, and the other plate-like beam 5, or a bolt head 6a protruding at least in the overhanging area 5a of the fixing bolt 6 without being caught in them. This prevents the adhesion of the metal piece.