Provided are an artificial dura mater having a laminated constitution of at least two layers of in vivo degradable polymers, at least one layer of them being a substrate layer, the substrate layer being formed of a lactic acid/glycolic acid/.epsilon.-caprolactone copolymer, the copolymer having a component molar ratio of 60-85:3-15:10-30 mol % and the copolymer having an average chain length that satisfies the following expressions (1) to (3) and a process for the production thereof, and when this artificial dura mater is used, no liquid leakage is caused since the bloating of suture holes is small, and the period of time for which it retains its strength is suitably a little longer than the period of time required for the regeneration of an autodura mater, 2