In this study, alginic acid that had an high affinity for a heavy metal and was noted for biological adsorbent was modified by an oxidizer, KMnO4. Chemical modification changed hydroxyl of the alginic acid into carboxyl and compare with alginic acid, modified alginic acid exhibited a characteristics that carboxyl groups are comparatively high. For the use of them as an adsorbent, beads were prepared by dropping alginic acid and modified alginic acid solution in dilute 2 wt% CaCl2 solution for non water soluble.The amount of removed Cu2+ and Pb2+ by modified alginic acid beads showed 84.7 mg and 90.9 mg per gram of beads, respectively. And it showed the amount of adsorbed heavy metal ions 10~20% higher than that of alginic acid beads in range of pH 4~7. In particular, modified alginic acid have a good adsorption capacity for Cu2+ and Pb2+ by Freundlich adsorption isotherm.According to this study, it is verified that alginic acid that is a nature high molecular substance improved capacity for actual application by increased heavy metal adsorption capacity by chemical modification.