The purpose of the present invention is to provide a heat generator that comprises an adhesive layer containing a volatile component and in which the volatile component is maintained in a stable state during storage, the volatile component is prevented from adhering to a heat-generating section, and it is possible to achieve an excellent warming effect during use. This heat generator comprises: a heat-generating section, an accommodation body that accommodates the heat-generating section and comprises an attachment surface to which an attachment body is attached, an adhesive layer provided to the attachment surface side of the accommodation body, and a release sheet provided to the attachment surface side of the adhesive layer. As a result of including a volatile component in the adhesive layer and providing a metal foil membrane to the release sheet, it is possible to maintain the volatile component in a stable state within the adhesive layer during storage. It is thereby possible to prevent the adhesion of the volatile component to the heat-generating section during storage and to achieve an excellent warming effect during use.