The effect of a bubble on the virtual current of an electromagnetic flow meter is studied numerically with the bubble at various positions along the pipe axis of the flow meter. To solve the distribution of the virtual current, a two-dimensional (2D) assumption is used. The domain is divided into sub-domains. In each of the sub-domains, the potential of the virtual current is expressed in series with unknown coefficients. An alternating method is used to find the unknowns. Various bubble sizes and bubble positions along the pipe axis of the flow meter are considered in the calculation. The change of the virtual current caused by the existence of the bubble is evaluated using deviation and asymmetry.