Hamamatsu has developed a 96-channel electrode array system that is mounted on the FDSS/?CELL. It adds electric field stimulations (EFS) to all 96 wells in a microplate simultaneously while fluorescence/luminescence signals are monitored. We measured oscillations of intracellular Ca2+ concentration, which occurs along with the beating of the cells, with a calcium sensitive fluorescent dye in human iPSC-derived cardiomyocytes (Cor.4U, Axiogenesis AG). We observed that the Ca2+ oscillation in cardiomyocytes was synchronized to the electric stimulation, which indicates that the EFS system is able to pace the beating of cardiomyocytes. We also observed that the Ca2+ oscillations in the presence of some ion channel blockers were modulated by adding EFS. Use of EFS coupled with intracellular Ca2+ kinetics measurements, in the high-throughput manner, should be useful in in vitro assessment of cardiac toxicity of pharmacological compounds using cardiomyocytes, in particular in toxicity screening at early stages of drug development, as well as in cardiomyocyte research.