To provide a heat-generating device which can be attached to clothing with sufficient adhesive force, even if the heat-generating device which has been previously attached to the clothing is reattached.

The heat-generating device 1 which can be attached to clothing after having been attached to the clothing includes: a pouch 2 which houses a heat-generating composition A including an oxidizable metal able to generate heat through contact with the air and has air permeability on one surface; an adhesive layer 3 formed on the other side of the pouch 2; and a first peeling sheet 4 pasted on the adhesive layer 3 so as to cover the adhesive layer 3. The first peeling sheet 4 has end sheet parts 41a, 41b for covering the ends 31a, 31b opposing each other on the adhesive layer 3, respectively; and a central sheet part 42 for covering a central part 32 sandwiched between the ends 31a, 31b of the adhesive layer 3. The end sheet parts 41a, 41b and the central sheet part 42 can be separately peeled from each other.