PROBLEM TO BE SOLVED: To provide a denitrification treatment method for nitrate nitrogen, even if potassium, iron and phosphorous are not included in the waste water to be treated, the treatment of nitrate nitrogen is inexpensively made possible even without adding a medicine as a nutrient, separately, and a device therefor.SOLUTION: Sulfur denitrification bacteria are carried on a packed bed 10 obtained by mixing a granular or lumpy porous mixture essentially consisting of sulfur and calcium carbonate with granular or lumpy, spherical limestone, and waste water 11 including nitrate nitrogen is passed into the packed bed 10 on which the sulfur denitrification bacteria are carried, thus the nitrate nitrogen included in the waste water is denitrated.
