To provide a flexible wiring board which maintains high insulating reliability as a conventional wiring board dose, offers high wiring adhesion, and enables the formation of fine pitch wiring; and to provide a manufacturing method for the flexible wiring board.

According to the flexible wiring board, a wiring pattern composed of a substrate metallized layer (12) having solubility characteristics different from that of copper, a copper metallized layer (22), and a copper plating layer (41) is fixed to an insulating film (1) via a metal diffusion layer (3) which is a product of denaturation of the insulating film (1) that results from the formation of the substrate metallized layer (12). In a plan view, the outline of the metal diffusion layer (3) fringes the outline of the copper plating layer (41), copper metallized layer (22), and substrate metallized layer (12), so that the metal diffusion layer (3) extends along the periphery of the copper plating layer (41), copper metallized layer (22), and substrate metallized layer (12).

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