A probe includes a transducer unit including a plurality of transducers which are arrayed in the first direction, transmit ultrasonic waves and receive echo signals, and a moving mechanism for continuously moving the transducer unit in the second direction crossing the first direction. A movement control unit controls the moving mechanism to continuously move the transducer unit in the second direction. A transmission unit causes the transducer unit to generate ultrasonic waves. A scan line signal generation unit generates a plurality of actual measurement scan line signals by delaying and adding a plurality of echo signals from the transducer unit. A scan line signal calculation unit calculates a plurality of mathematical scan line signals constituting a plurality of mathematical electronic scan planes from the plurality of actual measurement scan line signals. An image generation unit generates multislice tomograms on the basis of the plurality of calculated mathematical scan line signals.
