In this paper, we argue about miniaturization of circularly polarized wave patch antenna with cross-shaped slits. By comparing result of analysis to result of experiment, we check the adequacy of FDTD method, and we set up some notches or some cross-shaped slits on the patch antenna to make it small, and we consider miniaturization of circularly polarized wave patch antenna quantitatively by FDTD method. As a result we show 60% miniaturization when we set up four 12mm notches and we show 50% miniaturization when we set up four 12mm cross-shaped slits. Furthermore patch antenna has a high order mode resonance when we set up some notches or cross-shaped slits. We show the factor of this resonance.