To provide a highly strong protective sheet capable of preventing a collision with a guardrail by improving nighttime visibility for an automobile or a person, without requiring repaint or repair work on the areas of the guardrail with flaking paint or slight damage such as a scratch after removing metallic pieces sticking to the guardrail, while preventing an accident resulting in injury or death by preventing sticking of a metallic piece to the guardrail after tearing off from an automobile's outer steel sheet.

This highly strong protective sheet has a reflection material 3 on one surface of a fabric web 2 composed of highly strong fiber, and can be installed so as to cover a joint 5a and a bolt fastening part 5b of the guardrail 5 by applying a pressure sensitive adhesive 4 to the other surface of the fabric web 2.