PURPOSE: To miniaturize an antenna with a simple constitution, by forming a straight or curved slit in symmetry to a straight line connecting a center of a patch antenna and a feeding point, for decreasing the resonance frequency.

CONSTITUTION: The straight or curved slits 6a∼6c are provided symmetrically to an axial line 5 tying the center of a patch antenna 1 and the feeding point 3 in the edge direction therefrom. Further, slits 7a∼7c are provided respectively from the edge direction to the axial line 5, and the respective slits 6a∼6c or 7a∼7c are formed on a dielectric 2 together with the antenna 1. A slit 8 is provided at the opposite side of the feeding point 3 to the center of the antenna 1, a slit 9 is provided between the center and the feeding point 3, and a slit 10 is provided at the opposite side of the center of the antenna 1 and the feeding point 3. Thus, the resonance frequency is decreased and the microstrip antenna is miniaturized with a simple constitution.