To provide a bolt looseness inspection method capable of shortening the inspection time and reducing the inspection cost in looseness inspection of a bolt for fastening a structure.

In the looseness inspection of the bolt for fastening the structure, the bolt and a steel product of a bolt mounting part are preliminarily marked with a paint excellent in weather resistance at the time of fastening the bolt. In the looseness inspection of the bolt, the bolt part is enlarged from an image of the structure taken from the ground, and the looseness of the bolt that is an inspection object is determined by the slippage of line between the marking applied to the bolt and the marking applied to the steel product of the bolt mounting part.