A circuit board that has flexibility owing to an organic insulating layer and that still has high adhesion between metal wiring and the organic insulating layer; and a method for producing the circuit board without employing photolithography. The circuit board comprising a metal wiring arrangement portion and a metal wiring non-arrangement portion, wherein: in the metal wiring arrangement portion, metal wiring, a first diffusion layer, and a first organic insulating layer are stacked; in the metal wiring non-arrangement portion, a metal oxide layer, a second diffusion layer, and a second organic insulating layer are stacked; the metal wiring is made of a first metal element; and the first diffusion layer contains the first metal element and a second metal element.