A beamforming method includes generating a control signal for implementing a delay time for each of a plurality of transducers of each of a plurality of two-dimensional (2D) transducer-arrays, transmitting the control signal to a plurality of driving units respectively corresponding to the plurality of 2D transducer-arrays via an interposer that electrically connects the plurality of 2D transducer-arrays to each other, and driving each 2D transducer-array of the plurality of 2D transducer-arrays with a corresponding driving unit of the plurality of driving units according to the control signal transmitted via the interposer.