In this paper a technique that hybrid FDTD and ADI-FDTD methods for a locally graded mesh is proposed for efficient numerical modeling of RF/microwave structures. In it, the conventional FDTD grid is applied in the coarse mesh region, while the ADI-FDTD is used in the locally dense region. In comparisons with the conventional FDTD, the hybrid method results in the reduction of CPU time due to the unconditional stability of the ADI-FDTD and the minimum memory requirement because of the fewer components with the conventional FDTD algorithm. Numerical examples are given for validation.