Disclosed is a heat-activated adhesive sheet which includes a heat-activated adhesive layer, and two release liners arranged so as to sandwich and protect the heat-activated adhesive layer. One of the two release liners is a release liner containing a polyolefinic film as a base material, and the other is a release liner containing a polyester film as a base material. This heat-activated adhesive sheet has a transfer heat-activated adhesive layer, can thereby have a small thickness, is unlikely to suffer from “unintended separation”, and is unlikely to cause lifting and delamination of release liners when the sheet is stored as a roll.