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, which comprises forming a hole in a laminate comprising a first conductor layer, a layer (A) which is made of a fluororesin material containing a melt-moldable fluororesin having specific functional groups and a reinforcing fiber substrate and which has a dielectric constant from 2.0 to 3.5, a second conductor layer, an adhesive layer and a layer (B) made of a cured product of a thermosetting resin laminated in this order, applying, to an inner wall surface of the hole, 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.