To produce a wiring substrate having excellent electrical characteristics with conduction failure in a hole formed in a layer made of a fluororesin material sufficiently suppressed without conducting an etching treatment using metal sodium. A process for producing a wiring substrate 1, which comprises forming a hole 20 in a laminate comprising a first conductor layer 12, a layer (A) 10 which is made of a fluororesin material containing a melt-moldable fluororesin (a) having specific functional groups and a reinforcing fiber substrate and which has a dielectric constant of from 2.0 to 3.5, a second conductor layer 14, an adhesive layer 16 and a layer (B) 18 made of a cured product of a thermosetting resin laminated in this order, applying, to an inner wall surface 20a of the hole 20, either one or both of a treatment with a permanganic acid solution and a plasma treatment without conducting an etching treatment using metal sodium, and then forming a plating layer 22 on the inner wall surface 20a of the hole 20.