A method for determining an array space of an array antenna by using a genetic algorithm and an array antenna having a soft structure with irregular array spacing are disclosed. The array antenna having a sofa structure with irregular array spacing, includes: a plurality of radiation elements having an inclined angle based on a horizontal plane and arranged with irregular array spacing for radiating and receiving an radio wave; a plurality of phase shifters for amplifying radiation signals radiated from the plurality of radiation elements and receiving signals received from the plurality of radiation elements, and controlling phases of the radiation signals and the receiving signals; and a radio wave signal coupler for dividing a transmitting signal to the radiation signals, transferring the divided radiation signals to the plurality of phase shifters and coupling the receiving signals from the plurality of phase shifters.