A circuit substrate (3) is provided with first and second rigid parts (11, 12) having six metal foil layers, and a thin flexible part (13) having two metal foil layers connecting the two rigid parts. A ground wiring (51) which is shaped like a wide strip is formed on the surface metal foil layer, and a plurality of inter-rigid-part wirings (55) are formed on the inner metal foil layer in parallel lines. Outer edges (51a) of the ground wiring (51) are positioned closer to side edges (13a) of the flexible part (13) than to the inter-rigid-part wirings (55). The ground wiring (51) protects the inter-rigid-part wirings (55) from cracks.