PURPOSE: To improve the designing ability for the antenna by forming a slit in a ground conductor between antenna elements in a 1st group and antenna elements in an adjacent 2nd group, and lowering a 1st side lobe level.

CONSTITUTION: The printed array antenna is provided with strip conductors 12 and 13 formed on one surface of an insulator substrate and the groups consisting of the antenna elements 10 and 11, formed relatively with the microstrip lines, at an interval; and the slit 22 is formed in the ground conductor between the strip antenna elements 10 and 11 to suppress electromagnetic field coupling between the strip antenna elements. The strip antenna elements 10 and 11 are therefore excited by the electromagnetic coupling with a transmission line to provide desired characteristics. The linear strip antenna elements 10 and 11 are strong in the lengthwise coupling between the elements, so the slit 22 is provided at right angles to the length direction of the antenna elements 10 and 11.