PURPOSE:To prevent the top of a furnace from being heated a high temperature and to save the amount of hot air to be supplied, by charging coke from the top of a shaft furnace into the furnace, blowing hot air and pulverized coal through a tuyere into the furnace, and keeping the temperature of gas produced at the top to a proper temp. CONSTITUTION:Lump or particulate coke is charged from the top 2 of a shaft furnance 1 into the furnace 1 utilizing a blast furnace. Hot air heated to 1,000 deg.C in a hot-air oven 4 and pulverized coal are blown through a tuyere 3 into the furnace. When gasification proceeds and temperature within the furnace is elevated, high- temperature gas produced is drawn out from the belly 3' of the furnace, and mixed with hot air to be blown into the tuyere 3, whereby the temp. of produced gas to be recovered from the top 2 is kept at about 700 deg.C. EFFECT:Handware fitted in the neighborhood of the top of the furnace is prevented from being damaged by heat.