PROBLEM TO BE SOLVED: To provide an apparatus and method for wastewater treatment capable of decomposing an organic material at a high speed by preventing the inhibition of a sulfate-reducing bacterium by a sulfide in an anaerobic treatment environment and favorably growing the sulfate-reducing bacterium. SOLUTION: The apparatus for wastewater treatment includes: an organic material concentration measuring device 3 which measures the concentration of the organic material of discharged water to be treated; an infusion pump 5b which adds a sulfate 5a to the discharged water to be treated so that the concentration of a sulfate ion is higher than one-third of the concentration of the organic material; a reaction vessel 2 which decomposes the organic material holding the anaerobic bacteria and taking in the discharged water to be treated; a sulfide concentration measuring device 6 which measures the concentration of the sulfide of the treated water subjected to the decomposing process of the organic material thereof in the reaction vessel 2; and a blower 8b which blows a nitrogen gas from a nitrogen gas cylinder 8a to the reaction vessel 2 when the measured sulfide concentration is higher than a predetermined threshold, and when it is lower than the threshold, stops blowing the nitrogen gas. COPYRIGHT: (C)2011,JPO&INPIT