The present invention provides a heat-generating device which can be attached to clothing with sufficient adhesive force, even if such a heat-generating device which was previously attached to the clothing is reattached. The heat-generating device according to the present invention is provided with: an air-permeable pouch (2) on one side, which houses a heat-generating composition (A) including an oxidizable metal able to generate heat through contact with the air; an adhesive layer (3) formed on the other side of the pouch (2); a first peeling sheet (4) which is disposed on the adhesive layer (3) in such a way as to cover the adhesive layer (3); and a second peeling sheet (5) which is disposed on a first peeling sheet (4) in such a way as to cover the first peeling sheet (4). The first peeling sheet (4) comprises a peeling part (41) which is peeled together with the second peeling sheet (5) when the second peeling sheet (5) is peeled from the first peeling sheet (4), and a residual part (42) which remains on the adhesive layer (3) side.
