To provide a plastic fastening bolt that can fasten an object to be fastened by a proper axial force without using an expensive implement and a device in plastic fastening, and can easily be sorted whether it is not applied with plastic deformation yet, or applied with the plastic deformation already.

The plastic fastening bolt which fastens the object to be fastened until a shaft 4A of the bolt 4 is plastically deformed when initially fastening the bolt 4 has a detection-part embedding hole 5 which penetrates the bolt from a head 4 of the bolt to the shaft 4A of the bolt, and a detection unit 1 which detects that the shaft 4A of the bolt is deformed in the axial direction. The detection unit 1 is arranged in the hole 5 of the bolt 4 while axial tension is applied to the bolt 4 in advance.