The present invention provides a warmer in the form of a sheet shaped heat generating body which is obtained using a warming composition that generates heat when in contact with air, in which the warming composition can be easily dispersed and held in a uniform arrangement, and in which the warming composition is prevented from leaking; and provides a method for manufacturing such a sheet. The sheet shaped heat generating body pertaining to the present invention is obtained by supporting a warming composition and a heat-fusible adhesive powder on a nonwoven fabric (a), superposing a nonwoven fabric (b) on the upper surface, heating and pressing the assembly with the aid of a molding press, and impregnating the resulting sheet with water or an aqueous solution of an inorganic electrolyte.