PURPOSE: To simply and highly sensitively perform the quantitative determination of hydrogen peroxide, by allowing an alcohol and catalase to act on an H2O2-containing specimen and subsequently forcing luciferase to act on the resultant aldehyde in the presence of a long chain alkyl compound and FMNH2 to measure the amount of the emitted light.

CONSTITUTION: Catalase is allowed to act on a specimen containing hydrogen peroxide in the presence of an alkylalcohol (e.g., methanol) and the luciferase of a luminous bacterium (e.g., VIbrio harveyi) is forced to act on the produced aldehyde in the presence of a long chain alkyl compound (e.g., decane) and FMNH2 (reduction type flavin monoucleotide). The resultant light is measured with an usual emitted light-measuring apparatus such as a lumiphotometer to determine the quantity of the hydrogen peroxide in the specimen.