Disclosed is a biological desulfurization apparatus including a reaction tower 1 into which biogas generated by anaerobic fermentation of organic waste is to be introduced, a carrier-packed layer 2a, 2b arranged in the reaction tower and provided with a carrier to which microorganisms have adhered, an air feeding pipe 3 that mixes air into a lower part of the reaction tower, and a sprinkling mechanism 7 that sprinkles water on an upper part of the reaction tower, wherein the carrier-packed layer is arranged in two or more stages.