To provide an aqueous emulsion which shows a good initial adhesion, dry adhesion, water-resistant adhesion and heat-resistant adhesion and has no problem in its pot-life in actual use, and also provide its composition.

The aqueous emulsion for adhesives is an aqueous emulsion (1) obtained by emulsion polymerizing a monomer composition containing one or more monomers chosen from an aromatic vinyl monomer and a (meth) acrylate monomer, a hydroxyl group-containing vinyl monomer and an unsaturated carboxylic acid monomer using a surfactant. Here, the emulsion (1) has an average particle size of from 100 to 400 nm. The composition contains the aqueous emulsion (1) and an isocyanate compound (2).