Epoxy resin composition for prepreg, prepreg, and multilayered printed wiring board

To provide an epoxy resin composition for prepregs for use in producing a printed wiring board, especially a multilayered printed wiring board, which generates no harmful substances upon combustion, is excellent in flame retardancy and soldering heat resistance after moisture absorption, and has excellent high-temperature rigidity. [MEANS FOR SOLVING PROBLEMS] The epoxy resin composition comprises: a polyfunctional epoxy resin having 2.8 or more epoxy groups on the average per molecule and containing 20-55 mass%, based on the whole epoxy resin, pre-reacted epoxy resin obtained by reacting beforehand a phosphorus compound having, per molecule, from 1.8 to less than 3 phenolic hydroxy groups on the average and 0.8 or more phosphorus atoms on the average with a specific bifunctional epoxy resin (selected among biphenyl, naphthalene, dicyclopentadiene, and other types) in an epoxy group/phenolic hydroxy group equivalent ratio of (1.2 to 3, excluding 3)/1; a hardener comprising a dicyandiamide and/or a polyfunctional phenol compound; and an inorganic filler having a heat decomposition temperature of 400 DEG C or higher. The composition is used in a prepreg for the production of printed wiring boards.