An ultrasonic device provides a wider image to a user of the device and includes a transducer for transmitting a plane wave; and a processor for controlling the transducer to sequentially transmit plane waves in a plurality of different travelling directions and thereby extend a transmission range in which the plane waves travel, where the transducer receives a plurality of ultrasonic signals which are reflected from an object by each of the transmitted plane waves, and the processor synthesizes the plurality of received ultrasonic signals so as to image at least a predetermined partial region in the extended transmission range.