The quantity of formate was determined using apparatus comprised of a reactor with immobilized formate dehydrogenase (FDH) in the flow line. NADH formed by an enzymatic reaction was fluorometrically detected. The optimal concentration of NAD⁺ in the carrier was determined. The maximum peak area due to NADH was observed at pH 7.0 when the pH of the carrier consisting of piperazine-1,4-bis (2-ethanesulfonic acid) (PIPES) buffer ranged from 6.0 to 8.0. Various buffer types were also examined as carrier media at pH 7.0 and PIPES buffer showed the maximum peak area. When the carrier composed of PIPES buffer (0.1 M, pH 7.0) was used, the calibration curve for formate was linear in the range of 0.5-50 μM (r=1.000). Relative standard deviations of the peak area at 1 μM and 10 μM were 2.6% (n=7) and 1.6% (n=7), respectively. This method was applied to the analysis of formate in foodstuffs, and formate content determined by this method agreed with that determined by a commercially available test-kit.