Brewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water-based magnetic fluid stabilized perchloric acid. The magnetically modified yeast cells were characterized by scanning electron microscopy (SEM). Cu2+ biosorption properties of magnetically modified yeast cells from synthetic solutions were utilized in a continuous magnetic system. The Cu2+ ion-binding capacity decreased drastically with the increase of the flow rate. The maximum Cu2+ biosorption capacity was obtained to be 1.2mmol/g at 25 degrees C. Biosorption of Cu2+ increased with increasing pH and then reached almost a plateau value around pH 4.0. The yeast biomass can be easily regenerated by 0.1M HNO3 with higher effectiveness. Biosorption of heavy metal ions from artificial wastewater was also studied. The biosorption capacities are 0.92mmol/g for Cu2+, 0.52mmol/g for Hg2+, and 0.28mmol/g for Ni2+. Magnetically-modified yeast cells exhibits the following metal ion-affinity sequence: Cu2+Hg2+Ni2+.