Abstract: A body warmer for heating a human body by means of exothermic heat which consists of a particulate exothermic substance containing a main constituent for reducing a metallic oxide with the air and water content externally supplied for heating the body by the chemical reaction thereof, a fibrous agricultural solid waste impregnated with sodium chloride, bitter or composition salt, and an air permeable bag for filling the exothermic substance and the fibrous agricultural solid waste. Thus, the body warmer can heat at safe and effective temperature continuously for extremely long time so as to cure even neuralgia.