PURPOSE: To produce sintered ore having high quality by supplying high temp. air to the sintering raw materials compounded with coke in the firing zone and calcining and heat holding zone in an ignition furance or heat holding furnace and waste gases to said raw materials in a drying and preheating zone respectively from a heat exchanger.

CONSTITUTION: The high-temp. air obtained by blasting 13 to the heat exchanging medium 10 in a heat exchanger 10 heated with a burner 11 for the heat exchanger is fed 8 to the firing zone 2b and calcining and heat holding zone 2c in an ignition furnace, etc. 2 and is supplied 7a respectively to the surface layers of sintering raw materials 1. The preferable temp. of the high-temp. air is in a 800W1,300°C range higher thanthe firing temp. for coke. The waste gases of a low content of O2 of the heat exchanger 6 is supplied 7a to the drying and preheating zone 2a of the furnace 2 to dry and preheat the surface layers of the raw materials. Then, the coke in the raw materials 1 is fired by the high temp. air supplied to the zone 2b and the zone 2c; at the same time, sintering reaction is accelerated.