In an ultrasound diagnosis apparatus, a plurality of sub arrays are defined on a 2D array transducer. A plurality of groups are defined for each sub array. Each group is basically composed of a plurality of transducer elements which are connected in parallel with each other. A sub array shape is variably defined for a plurality of sub arrays in accordance with the beam direction and the depth of a focal point. Further, a grouping pattern is variably defined for each sub array. The acoustic distances between the respective transducer elements and the focal point is made as equal as possible for a plurality of transducer elements forming each group, whereby a preferable beam profile can be obtained.