In the present investigation, preparation, purely isolation and physicochemical properties of hemocyanin from fluid of Paralithodes camtschatica by ultracentrifugation and electrophoresis are reported and discussed. The hemocyanin was precipitated by adding ammonium sulfate to 100 % of saturation. The ppt of protein was dialysed against water to remove all (NH4)2SO4 and insoluble materials were removed. The resulting hemocyanin solution was purified by precipitation at isoelectric point several times. The final purified precipitation was dialysed against acetate buffer at pH 6.0, precipitates were removed and subjected to measurements. From ultracentrifugal measurements, in 0.5 M acetate+0.5 M NaCl at pH 6.1 presence of two components was recognized. In 0.1 M acetate+0.1 M NaC1 at pH 6.2, however, the components have reduced to single peak. Also it was observed that over the ionic strength range 0.1~0.2 and the pH range 5.0~6.2, the hemocyanin molecule has consisted of single component and the obvious differences in sedimentation const. under the each condition were not apparent. In 0.1 M carbonate buffer pH 8.8, a main peak (about 90 %) having sed. const. S20=6 to 7, which have about one half value in above acetate buffer, was observed. From the above it was concluded that the component having greater sedimentation constant corresponds to whole protein molecule.