Disclosed is an electronic scanning array antenna which can be used as a UWB radar having an occupied band of not less than 500 MHz. An impulse generator is connected to each of a plurality of antenna elements constituting the electronic scanning array antenna, and a transmission trigger time to each of the impulse generators connected to the antenna elements is changed, whereby the phase of radio waves emitted from an antenna is equivalently changed. Moreover, a transmission trigger repletion interval is changed to thereby control a direction of a beam emitted from the array antenna. As means of changing a transmission trigger timing to each of the impulse generators connected to the antenna elements, a method of changing a frequency of a transmission trigger pulse and a method of changing a pulse position are adopted.