A modification of microdiffusion method for the determination of nitrate are described. Nitrate is satisfactorily determined by reduction of the nitrate to ammonia with powdered Devarda's alloy instead of titanous sulphate solution and subsequent distillation with magnesium oxide, both the reduction and distillation being carried out in a Conway microdiffusion unit incubated in a incubator at 30℃. The procedure is identical to that of the previous method only except for a substitution of suspension of powdered Devarda's alloy for titanous sulphate solution. A fraction of powdered Devarda's alloy, guaranteed reagent, smaller than 150~200 mesh is suspended in a distilled water and 1 ml of the suspension containing 50~75 mg of the alloy per ml is added to each unit. The incubation period necessary f o r complete recovery of the nitrate is 24~30 hr for a salt solution of lower concentration and about 36 hr for that of higher concentration, such as 1 N KCl. The suitable size of sample solution is up to 120 μg of nitrate-N (or ammonium-N plus nitrate-N) in 2 ml. The recoveries b y the recommended procedures of the nitrate added are between 98 and 100% and somewhat superior to those by the method using titanous sulphate solution. The results showed that several colorimetric, distilling or aerating methods for the determination of nitrate have been proposed, but the method presented here might be more excellent, because this method is simple, easy, accurate and applicable to colored solution and to a large number of samples.