Foamable epoxy resin composition

A foamable epoxy resin composition comprising

• (A) 100 parts by weight of a liquid epoxy resin having at least one epoxy group in the molecule,
• (B) 0.5-20 parts by weight of a latent curing agent for epoxy resin selected from the group consisting of an imidazole, an isophthalic acid dihydrazide, an N,N-dialkylurea, an N,N-dialkylthiourea, tetrahydrophthalic anhydride, isophoronediamine, m-phenylene diamine, N-aminoethylpiperazine, a boron trifluoride complex compound and trisdimethylaminomethylphenol,
• (C) 0.5-15 parts by weight of a foaming agent having a decomposition temperature of 100.degree.-220.degree. C.,
• (D) 0.5-5 parts by weight of an anionic surface active agent, and
• (E) 10-200 parts by weight of at least one rubbery elastomer insoluble in said epoxy resin at room temperature by miscible with and dispersible in said epoxy resin at temperatures of 80.degree.-150.degree. C. and selected from the group consisting of a chloroprene rubber, a butadiene-acrylonitrile rubber, a carboxyl-modified butadiene-acrylonitrile rubber, an epoxy-modified butadiene-acrylonitrile rubber, a butadiene rubber and an isoprene rubber,
• which composition has a melt viscosity of 2.5.times.10.sup.3 -5.times.10.sup.4 dPa.multidot.s at the decomposition temperature of said foaming agent.