Provided are a matrix resin composition for fiber reinforced plastic, which comprises a bifunctional or trifunctional liquid diisocyanate, a bifunctional polyol and a bifunctional chain extender containing an active hydrogen group, with a molar ratio of the functional groups of the diisocyanate, polyol and chain extender of 5.0 to 1.0:1.0:4.0 to 0, respectively; and a process for producing fiber reinforced plastic, which comprises impregnating a fibrous material with the resin composition and then curing. The present invention makes it possible to produce a molding containing fibers densely, having excellent strength and inflatability, in the production of an FRP molding by using a thermosetting resin having an extended pot life.