A new simple method for the spectrophotometric determination of Pb(II) in fly ash leachates was developed. These leachates tend to contain a large amount of Ca(II) and Zn(II); this interferes with spectrophotometric determination of Pb(II) when conventional colorimetric agents are used. A copolymer consisting of protoporphyrin IX disodium salt and acrylamide was synthesized as a colorimetric agent. A measuring reagent containing ethylenediamine-N,N'-dipropionic acid (EDDP) as a masking agent for Zn(II) and an appropriate amount of Ca(II) together with the copolymer was applied to determine Pb(II). The temporal change in the absorption spectrum of the measuring reagent was acquired with a newly developed portable spectrophotometer for this method. The composition of EDDP and Ca(II) in the measuring reagent was optimized to measure leachates contaminated with Ca(II) and Zn(II). The detection limit and relative standard deviation of Pb(II) measured using the optimized method were 0.05 mg L(-1) and 2.3%, respectively. The tolerance limits for Ca(II) and Zn(II) contaminants, where errors of less than 10% were allowed at a concentration of 0.5 mg L(-1) Pb(II), were 4000 and 4 mg L(-1), respectively. The determination of Pb(II) in various samples of actual leachates from incinerator fly ash was examined with this method. The obtained values correlated well with those obtained by flame atomic absorption spectroscopy.