Provided is e.g., an epoxy resin curing agent, an epoxy resin composition and a gas-barrier adhesive containing the epoxy resin composition which can express high gas-barrier properties and excellent adhesiveness to various types of plastics, in particular, to polyester, and a gas-barrier laminate having high gas-barrier properties and excellent adhesiveness to various types of plastics, in particular, to polyester. The epoxy resin curing agent of the present invention contains at least the following component (I) and component (II) in a mass ratio [component (I)/component (II)] of 50/50 to 92/8. Furthermore, the epoxy resin curing agent of the present invention contains at least an epoxy resin and the epoxy resin curing agent of the present invention. Component (I): a reaction product obtained by reacting at least (A) metaxylylenediamine or paraxylylenediamine and at least one selected from (B1) acrylic acid and acrylic acid derivatives; Component (II): a reaction product obtained by reacting at least (A) metaxylylenediamine or paraxylylenediamine and at least one selected from (B2) unsaturated carboxylic acids represented by the following formula (1) and derivatives thereof: wherein R 1 and R 2 each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aralkyl group having 1 to 8 carbon atoms or an aryl group; with the proviso that at least one of R 1 and R 2 is an alkyl group having 1 to 8 carbon atoms, an aralkyl group having 1 to 8 carbon atoms or an aryl group.