To provide a compact hot blast generating device, in which combustion assisting gas of high temp. of ≥1300°C, can be manufactured with high energy efficiency.

At least one pair of blasting tuyeres 2 with a combustion chamber 4 and a heat accumulator 5 disposed on the back side of a tuyere main tube 3, are arranged in a reaction furnace, and also, one tuyere sucks a gas generated in the furnace and the combustible component in the generated gas is burnt in the combustion chamber 4. Then, this combustion exhaust gas is introduced into the heat accumulator 5 and while accumulating the sensible heat of the combustion exhaust gas into a heat accumulating body, the other tuyere introduces the combustion assisting gas for using in the reaction furnace into the heat accumulator 5 to heat the combustion assisting gas by heat exchange with the heat accumulating body. Such an operation as to blast the combustion assisting gas into the reaction furnace through the tuyere main tube 3 is alternately executed by both tuyeres, and thus, the compact hot blast generating device, in which the combustion assisting gas of the high temp. can be obtd. with high energy efficiency is provided.