PURPOSE: To remove a measuring error due to a reflected wave, by mounting an element electric field calculation means and a correction and calculation means of an aperture surface exciting distribution to a measuring apparatus.

CONSTITUTION: A measuring apparatus uses an element exciting condition altering means 5 capable of indivisually changing and fixing the exciting conditions of radiation elements 9-1W9-N forming an array antenna and a position control means 6 capable of moving and setting a neighbourhood field measuring antenna 1 to a position necessary for measurement to measure the aperture surface exciting distribution of the array antenna. Further, an element electric field calculation means 8 receives the exciting condition to an element to be measured from the element exciting condition altering means 5 and the radiation neighborhood field detected by the measuring antenna to calculate aperture surface exciting distribution from the detected electric field corresponding to the exciting condition. A correction and calculation means 11 calculate a fixed electric field component and an electric field component of which the phase rotates at equal amplitude from the input of at least three different receiving electric field data detected by the measuring antenna 1 and, on the basis of the calculated results, the aperture surface exciting distribution obtained by the element electric field calculation means 8 is corrected.