PURPOSE: To enhance the scanning line density without enlarging a circuit scale by selecting a vibrator group of a desired aperture portion from plural vibrators, dividing it into plural blocks consisting of a prescribed number of pieces of vibrators, and connecting each block to a transmitting/receiving circuit of a one-channel portion.

CONSTITUTION: A probe 2 is constituted at a minute vibrator pitch so as to obtain high scanning line density at the time of enlargement to the maximum, and by a first selecting circuit 3, 16 pieces of continuous vibrators E1-E16 are selected from all vibrators E1-E64 in order to form a desired ultrasonic beam. By switching the selection of the vibration group by this first selecting circuit 3, an electronic scan of an ultrasonic wave can be executed. Subsequently, the vibrators E1-E16 in the vibrator group selected first by a second selecting circuit 4 are subjected to blocking by plural pieces each, and also, each block is connected so as to become one channel, and they are selected to transmitting receiving circuits 5a-5d of every channel. In such a way, the number of driving vibrators per one beam can be increased by exceeding the limit of the number of channels of the device 1, and the scanning line density can be enhanced without increasing the circuit scale.