PURPOSE: To make it possible to provide an antenna element with interchangeability corresponding to characteristics of an oscillating element, by incorporating a function of changing over bias voltages of the oscillating element in the antenna elements of an array antenna with a built in exciting source.

CONSTITUTION: Element antennas 21∼2n set in array are excited by semiconductor oscillating elements 3 (3a1, 3b1∼3bm, and 3ae) bult in antenna elements 11∼1n respectively to emit a radio wave. When two kinds of oscillating elements 3 differing in breakdown voltage and operating voltage are used, voltages of bias electric power sources 9a and 9b are used as two kinds of breakdown voltages and selected via change-over switches 71∼7n inside antenna elements 11∼1n accordance with oscillating elements 3. Pulse driving voltages generated by driving circuits 41∼4n are superposed upon the above-mentioned bias voltage by the superposing circuit and applied to oscillating circuit 3.