A three-dimensional ultrasonic imaging apparatus, comprising: a signal generating portion for generating a driving signal; an ultrasonic transducer in which a plurality of piezoelectric vibrators are disposed in a matrix or a linear array; a driving element selecting portion connected to the piezoelectric vibrators for selecting a piezoelectric vibrator to emit ultrasonic waves from the ultrasonic transducer by selectively driving a plurality of piezoelectric vibrators; a signal detecting circuit configured to cause an ultrasonic wave emitted by the piezoelectric vibrator selected by a starting element selecting portion to enter an object to be inspected via an acoustic wave propagating medium, to receive the reflected echo from the object to be inspected, and then to detect an electric signal corresponding to the reflected echo; a signal processing portion configured to receive the electric signal corresponding to the detected echo, to perform image synthesizing of a state of the object to be inspected on the basis of a detection time with which the signal detecting circuit detects the driving signal of the piezoelectric vibrators as a reflected echo and matrix special arrangement of the piezoelectric vibrators, and to generate three-dimensional imaging data; and a display device configured to receive the three-dimensional imaging data from the signal processing portion and to display the result of the image synthesizing processing, characterized by a table data generating portion configured to generate table data in which one-way propagation time of one propagating direction from the piezoelectric vibrators, via the acoustic propagating medium, to each of three-dimensional imaging mesh elements corresponding to the three-dimensional imaging data in the object to be inspected, is stored as table data corresponding to each of the piezoelectric vibrators, to obtain two-way ultrasonic wave propagation time data by selecting a pair of table data, corresponding to a combination of the piezoelectric vibrators emitting and receiving ultrasonic waves to and from the three-dimensional imaging mesh element, and to perform the image synthesizing of the state of the object to be inspected on the basis of the obtained two-way propagation time. a signal generating portion for generating a driving signal; an ultrasonic transducer in which a plurality of piezoelectric vibrators are disposed in a matrix or a linear array; a driving element selecting portion connected to the piezoelectric vibrators for selecting a piezoelectric vibrator to emit ultrasonic waves from the ultrasonic transducer by selectively driving a plurality of piezoelectric vibrators; a signal detecting circuit configured to cause an ultrasonic wave emitted by the piezoelectric vibrator selected by a starting element selecting portion to enter an object to be inspected via an acoustic wave propagating medium, to receive the reflected echo from the object to be inspected, and then to detect an electric signal corresponding to the reflected echo; a signal processing portion configured to receive the electric signal corresponding to the detected echo, to perform image synthesizing of a state of the object to be inspected on the basis of a detection time with which the signal detecting circuit detects the driving signal of the piezoelectric vibrators as a reflected echo and matrix special arrangement of the piezoelectric vibrators, and to generate three-dimensional imaging data; and a display device configured to receive the three-dimensional imaging data from the signal processing portion and to display the result of the image synthesizing processing, characterized by a table data generating portion configured to generate table data in which one-way propagation time of one propagating direction from the piezoelectric vibrators, via the acoustic propagating medium, to each of three-dimensional imaging mesh elements corresponding to the three-dimensional imaging data in the object to be inspected, is stored as table data corresponding to each of the piezoelectric vibrators, to obtain two-way ultrasonic wave propagation time data by selecting a pair of table data, corresponding to a combination of the piezoelectric vibrators emitting and receiving ultrasonic waves to and from the three-dimensional imaging mesh element, and to perform the image synthesizing of the state of the object to be inspected on the basis of the obtained two-way propagation time.