Abstract: In the conventional finite-difference time-domain(FDTD) method, fine cells reduce the time-step size due to the Courant-Friedrich-Levy(CFL) stability condition, which results in an increase in computational effort, such as the central processing unit (CPU) time. In the alternating-direction implicit finite-difference time-domain(ADI-FDTD) method, a larger time-step size than allowed by the CFL stability condition limitation can be set because the algorithm of this method is unconditionally stable. Consequently, an increase in computational efforts caused by fine cells can be prevented. The simulation experiments data by the ADI-FDTD method were compared with that by the conventional FDTD method. The results show that simulation field by ADI-FDTD method agree quite well with that by the FDTD method, but the required CPU time can be much shorter than that for the FDTD method.