A heat generating device including a heat generating element and an enclosing material entirely enclosing the heat generating element. The heat generating element includes a base sheet formed of a fibrous sheet containing superabsorbent polymer particles and hydrophilic fibers and a layer of a heat generative composition containing oxidizable metal particles on a side of the base sheet. The enclosing material includes a first cover sheet and a second cover sheet bonded together in their peripheral portions to provide a space therebetween in which the heat generating member is placed. The heat generating element in the space is in a non-fixed state to the enclosing material. The first cover sheet has air permeability in part and is disposed on the side of the layer of the heat generative composition. The heat generating device is capable of releasing steam from the side of the first cover sheet during use.