An iron powder for an exothermic composition according to the present invention has a bulk density of 0.3 to 1.5 g/cm3. Furthermore, an exothermic composition according to the present invention contains the iron powder, a carbon material, a halide salt, and water. Furthermore, an exothermic body production method according to the present invention includes: forming a coated member by coating a base material sheet with a flowable exothermic composition containing the iron powder, a carbon material, and water; and adjusting an amount of moisture in the coated member by removing water from the coated member. Furthermore, the present invention is directed to a production method for the iron powder (an iron powder for an exothermic composition) including: a reducing step of reducing iron oxide to obtain reduced iron; and a step of milling the reduced iron. In the reducing step, the iron oxide is reduced by introducing iron oxide and a solid reductant with a volatile matter content of 10% by mass or more into a heating furnace whose internal portion contains no sulfur gas or is set to an air or inert gas atmosphere, and setting the internal portion to a reducing gas atmosphere through heating under a condition that an ambient temperature of the internal portion is from 900 to 1000° C.