PURPOSE: To recover most part of sulfur portion in H2S as sulfur without using a catalyst by reacting a gas containing H2S with O2 under a specific condition to convert a part into SO2 and further reacting the resultant SO2 with H2S.

CONSTITUTION: A feed gas 2 containing ≥50 vol.% H2S is passed through a train of at least 3 stages (10, 20, 30 and 40) provided with furnaces 12, 22, 32, 44 for generating sulfur vapor and steam by burning a part of H2S with oxygen 4, 24, 34, 44 for supporting combustion in each stage and reacting a part of the generated SO2 with the remaining H2S at ≥800°C, waste heat boilers 14, 26, 36, 46 and condensers 18, 29, 38, 48 for recovering sulfur vapor, up to 80 mol.% of H2S to enter in the furnace 12 is kept unreacted in the 1st stage 10 and ≥80 mol.% of sulfur portion of H2S in the supply gas 2 is finally converted into sulfur vapor and recovered.