In order to investigate the characteristics of electromagnetic flowmeter in two -phase flow, an AC electromagnetic flowmeter was designed and manufactured. In various flow conditions, the signals and noises from the flowmeter were obtained and analyzed by comparison with the observed flow patterns with a high speed CCD camera. The experiment with the void simulators in which rod shaped non-conducting material was used was carried out to investigate the effect of the bubble position and the void fraction on the flowmeter. Based on the results from the void simulator, two -phase flow experiments encompassed from bubbly to slug flow regime were conducted. The simple relation $Delta$ $U_{TP}$ = $Delta$ $U_{SP}$ (l-$alpha$) was verified with measurements of the potential difference and the void fraction. Due to the lack of homogeneity in a rent two -phase flow, the discrepancy between the relation and the present measurement was slightly increased with void fraction and also liquid volumetric flux jf. Whereas there is no difference in the shape of the raw signal between single-phase flow and bubbly flow, the signal amplitude for bubbly flow is higher than that for single -phase flow at the same water flow rate, since the passage area of the water flow is reduced. In the case of slug flow, the phase and the amplitude of the flowmeter output show dramatically the flow characteristics around each slug bubble and the position of a slug bubble itself. Therefore, the electromagnetic flowmeter shows a good possibility of being useful for identifying the flow regimes.ul for identifying the flow regimes.