The ADI method is applied to obtain the numerical solution of unsteady MHD flow through a rectangular channel under transverse magnetic field. The equations governing the flow consist of a system of two coupled parabolic equations in two dimensions. The velocity, induced magnetic field and the flux through the section have been worked out numerically at different time levels for various Hartmann numbers. The steady state results are compared with J. A. Shercliff’s exact solution [Proc. Camb. Philos. Soc. 49, 136-144 (1953; Zbl 0050.194)]. It is found that as the Hartmann number increases, the steady state is reached faster, the flux decreases and the velocity profiles show a flattening tendency.