A prepreg of FRP (fiber reinforced plastic) having with (i) a matrix resin composition containing a bifunctional isocyanate and/or a trifunctional isocyanate, a polyol and a bifunctional chain extender having two active hydrogen groups at a molar ratio, as a functional group, of isocyanate:polyol:chain extender=5.0 to 1.0:1.0:4.0 to 0, or containing a bifunctional isocyanate and/or a trifunctional isocyanate and a polyol at a molar ratio, as a functional group, of liquid isocyanate:polyol=0.9 to 1.1:1.0; and (ii) a fibrous material. A production process of the prepreg. According to the present invention, the prepreg has a sufficient pot life and permits convenient production of an FRP molding.