To provide an epoxy resin composition suitable as a matrix resin for fiber reinforcement, and a yarn prepreg suitable in unwindability, excellent in higher processability due to drapability, high in the tensile strength of the epoxy resin composition after curing, and high in efficiency of the strength of reinforcing fibers. A yarn prepreg, satisfying the following formulae (1) to (3): 50.ltoreq.Wf.ltoreq.80 (1) 20,000.ltoreq.F.ltoreq.100,000 (2) F/8,000.ltoreq.d.ltoreq.F/2,400 (3) where Wf is the content by weight of the fiber bundle (%), F is the number of filaments in the fiber bundle and d is the width of the prepreg (mm). An epoxy resin composition for a fiber reinforced composite material, comprising at least the following components [A], [B] and [C]: [A]: An epoxy resin mixture containing two or more epoxy resins, in such a manner that 100 weight parts of the epoxy resin mixture contains 40 to 79 parts of a monofunctional or bifunctional epoxy resin and 21 to 60 parts of a trifunctional or higher functional epoxy resin and that the epoxy resin mixture is 210 to 370 in epoxy equivalent weight [B]: Fine particles containing a rubber ingredient and insoluble in the epoxy resins [C]: A curing agent