Cadmium(II) complexation by a well characterized soil fulvic acid (FA) from the Okchun Metamorphic Belt were studied at pH of 6.0 in 0.1 M $NaClO_4$ using the ultrafiltration technique. The conditional stability constants thus obtained were log K= 3.90${pm}$0.15 and 3.99${pm}$0.12 $L{cdot}mol^{-1}$ at fulvic acid concentrations of 101 and 226 mg${cdot}L^{-1}$ respectively. When free cadmium ion concentration was measured directly using an ion selective electrode, log K of 4.12${pm}$0.03 $L{cdot}mol^{-1}$ was obtained. These results show that fulvic acid forms predominately 1 : 1 complex with $Cd^{2+}$ ions. The maximum binding ability of this polyelectrolyte material was 0.886 mmol Cd/g FA. The average gram formula weight of fulvic acid was estimated to be 1130 daltons.