To provide an array antenna stable in frequency without increasing the output of an oscillator or requiring an amplifier.

In the array antenna, which is provided with the oscillator, a driver means for dividing the output power of the oscillator, plural feeder circuits for feeding the divided output power and antenna elements provided for every power feeding circuit to radiate the power fed from the feeder circuits from the antenna elements to the space, the individual oscillator is located for every feeder circuits, and the oscillator feeds transmission power to be injected and synchronized through a divider or a coupler to each individual oscillator.