A preform, formed with a plurality of reinforcing fiber substrates stacked to each other and each made of at least reinforcing fiber yarns, has a resin material, whose main component is a thermoplastic resin, interlaminated between the layers of the reinforcing fiber substrates in the preform, and has through holes extending through a plurality of the reinforcing fiber substrates in the thickness direction of the preform; an FRP molded using this preform; and processes for producing these. By improving the impregnability in the thickness direction of the preform, an FRP excellent both in various mechanical properties and in matrix resin impregnation and stabler in quality can be produced with high productivity.