A method for the quantitative determination of polyamines, which comprises allowing a polyamine oxidizing enzyme, an .omega.-aminoalkylaldehyde dehydrogenase, an oxidized nicotinamide coenzyme and, as required, an acylpolyamine anidohydrolase to act upon a sample solution containing polyamines (for example, urine, blood and other kinds of body fluid), and measuring the reduced nicotinamide coenzyme thus formed by, for example, colorimetry, thereby determining the amount of said polyamines.