The critical behavior of the double perovskite La(2)NiMnO(6) was investigated by measurement of the magnetization around the Curie temperature T(C). The magnetic data were analyzed in the critical region using the Kouvel-Fisher method to yield the critical exponents of β = 0.408 ± 0.011 with T(C) = 270.50 (from the temperature dependence of the spontaneous magnetization below T(C)) and γ = 1.295 ± 0.015 with T(C) = 271.10 (from the temperature dependence of the inverse initial susceptibility above T(C)). The critical magnetization isotherm M(T(C),H) gives δ = 4.139 ± 0.090. The critical exponents obtained by this method obey the Widom scaling relation δ = 1+γ/β, implying the critical exponents are reliable. The values of critical exponents are close to those predicted by the three-dimensional (3D) Heisenberg model with short-range interactions.