To provide a thin layer reinforcement which improves the mechanical characteristics (tensile strength, tear strength, etc.) of a thin, lightweight, flexible substrate to be reinforced while its features including thickness, weight, and flexibility are kept.

The thin layer reinforcement 10 is a thin layer reinforcing tape made of a tape-shaped material in which a strengthening single yarn bundle 1 opened/widened to make its width per 1,000 yarns at least 1.3 mm is impregnated with an adhesive resin 11. The reinforcing tape 10 is laminated on the substrate 20 to be reinforced to reinforce the mechanical characteristics of the substrate 20.