PURPOSE: To equivalently measure a distant field radiation pattern by setting the same phase to all element antennas of a phased array antenna and placing them on a turntable to rotate them and measuring the synthesized reception level in accordance with the angle of rotation to correct the phase.

CONSTITUTION: Element antennas 1 are placed on a turntable 5, and a counter antenna 8 is installed in the Fresnel area for a phased array antenna 4 at the distance of a distant field area from each antenna 1. The set phase of each antenna is successively changed to measure the change of the synthesized reception level by a receiver 6. A calculating circuit 10 calculates amplitudes and phases of antennas 1 in accordance with calculated data. All antennas are set to the same phase, and the synthesized reception level corresponding to the angle of rotation of the turntable 5 is received. At this time, the circuit 10 calculates phase set values, which correct phase differences of radio waves incident on antennas 1, and gives them to phase devices 2. Thus, coming waves can be regarded as plane waves and the distant field radiation pattern is equivalently measured.