A resin composition including an epoxy resin (A), a curing agent (B), and vinyl polymer particles (C), in which the contained amount of epoxy resin (a1) having a molecular weight of 100-480 is 30-90 parts by mass per 100 parts by mass of the epoxy resin (A), the contained amount of epoxy resin (a2) having a molecular weight of 2,000-40,000 is 10-70 parts by mass per 100 parts by mass of the epoxy resin (A), the contained amount of the vinyl polymer particles (C) is 2-30 parts by mass per 100 parts by mass of the epoxy resin (A), and the instantaneous maximum thickening value of the vinyl polymer particles obtained by the following method is 0.3-5.0 Pa·s/° C.