To make it possible to effectively emit the radiation of the far IR radiative material used in a throw-away body warmer using the far IR radiative material to the outside without the hindrance by the exothermic material packed in a bag material and the bag material and to effectively exhibit the effect of far IR rays without the peeling and dislodging of the far IR radiative material applied to the bag material during use or the like.

The far IR body warmer 1 is constituted by packing the exothermic material 3 into the bag material 2 of, for example, a flat shape. This bag material 2 comprises a sheet 20 formed by using a nonwoven fabric 5 which is formed by using the fibers 4 obtd. by kneading the far IR radiative material 4a to a resin 4b, such as polyethylene(PE) or polypropylene(PP) and is adjusted in air permeability as the outermost layer, laminating a film 6 formed by providing PP with micropores on the inner side thereof and further laminating a PE film 7 having a good thermal fusion property on the inner side thereof. The other surface of the bag material 2 comprises a sheet 10 formed by using a PP film 8 which is a base material layer on the outermost layer and laminating the PE film 9 having the good thermal fusion property on the inner side thereof.