The compact high gain planar antenna composed of the inverted L antenna composed of the coplanar waveguide located on rectangular conducting plane is analyzed numerically. The parasitic conducting plane is located above the inverted L antenna. The design frequency is from 2.40 GHz to 2.50 GHz. When the antenna size is 44 mm by 63 mm by 6 mm (0.36 wavelength by 0.52 wavelength by 0.049 wavelength), S11 less than −10dB is satisfied at the frequencies from 2.39 GHz to 2.51 GHz. The directivity becomes more than 8 dBi at this frequency band. In the numerical analysis, the electromagnetic simulator “WIPL-D” based on the Method of Moments is used.