PURPOSE: To control a side reaction and efficiently recover sulfur by mixing a solid reducing agent with predetermined solid particles to form a moving bed and passing SO2-contg. air through the bed.

CONSTITUTION: An SO2-contg. gas is mixed with air fed from line 2 and introduced into moving bed reactor 3 through line 1. A solid reducing agent and solid particles are supplied to the top of reactor 3 from lines 4, 5, respectively to form a moving bed of 650W1,000°C in reactor 3. As the reducing agent coal or coke granules are used, and the solid particles are of one or more among Ca and Mg oxides, hydroxides and carbonates and iron oxide. The wt. ratio of the reducing agent to the particles is preferably adjusted to 1:(0.01W0.5). The mixed gas introduced into a lower part of reactor 3 rises while countercurrently contacting with the moving bed, and the contained SO2 is reduced to vaporous S, which is taken out to line 6.