The NAD(P)+ (Nicotinamide adenine dinucleotide phosphate) was electrochemically reduced to NAD(P)H (Nicotinamide adenine dinucleotide phosphate hydrogen) without enzyme catalyst by using the special electrode which functions as an electrochemical catalyst. The electrode was made from kaolin, graphite powder and Mn-ion by baking at 1200℃. The neutral red was covalently bound to the electrode without Mn-ion. The modified electrode with Mn-ion function as a catalyst for reduction of NAD+ to NADH and that with neutral red function as a catalyst for reduction of both NAD+ and NADP+ to NADH and NADPH, respectively. Nitrate was confirmed to be reduced to nitrite coupling with oxidation of NADH which was electrochemically reduced or NADH which was commercially purchased as a chemical. Nitrate biosensor is possible to be made with the catalytic electrode but without NAD+-reductase or dehydrogenase.