Abstract: A method for quantitative analysis of hydrogen peroxide at a high precision is disclosed. The method comprises reacting a divalent cobalt compound with hydrogen peroxide in the presence of peroxidase or a substance similar to peroxidase to produce a trivalent cobalt compound, reacting the trivalent cobalt compound thus produced with a trivalent cobalt indicator to produced a colored complex, and subjecting the colored complex to colorimetric quantitative analysis. The method enables various enzymatic activities producing hydrogen peroxide by the reaction with substrates as well as the amount or activity of substances involving the known enzymatic reactions linked with such enzymatic reactions, of enzymes and coenzymes, to be quantitatively determined very easily at a high sensitivity at a wavelength of above 600 nm without the interference of hemoglobin, bilirubin, or turbidity.