The present invention relates to an adhesive composition containing a base polymer and a moisture-curable component, wherein the base polymer contains a polymer having no functional group which reacts with the moisture-curable component, and a water content of the base polymer after storage at 25° C. and 50% RH for 24 hours is 0.1% by weight or less, and wherein the moisture-curable component is contained in an unreacted state, an adhesive layer made from the adhesive composition, and an adhesive sheet including the adhesive layer.