A technology for structuring a three-dimensional image in a more accurate position spatially even when an ultrasonic transducer unit does not perform oscillation scanning at completely constant angular velocity is disclosed. According to the technology, an oscillation angle detection means 104 detects an oscillation angle of an ultrasonic transducer unit 1, and a three-dimensional image processing means 11 forms a three-dimensional image based on the oscillation angle detected by the oscillation angle detection means and image data outputted from an ultrasonic receiving means 4.
