A warming device (1) includes a heat generating element (3) that contains a powder of an oxidizable metal (3a), a powder of a carbon material (3b), and a powder of a porous material (3c) other than the oxidizable metal (3a) and the carbon material (3b). The heat generating element (3) is a sheet material. It is preferable that, in the heat generating element (3), the ratio of the mass content of water to the mass content of the powder of the oxidizable metal (3a) multiplied by one hundred is from 30 to 270. It is preferable that, in the heat generating element (3), the ratio of the mass content of the porous material (3c) to the mass content of oxidizable metal (3a) multiplied by one hundred is from 1 to 30. It is preferable that, in the heat generating element (3), the ratio of the mass content of the porous material (3c) to the mass content of water multiplied by one hundred is from 1 to 30.