An ultrasonic imaging apparatus comprising: an ultrasonic receiver having a plurality of receiving elements (200-203, 312-314) for receiving ultrasonic waves reflected or generated inside a subject to generate a respective signal; a sampling means adapted to sample the respective signal received by at least a part of the receiving elements by a cycle of a clock to generate respective digital signals; a receive beam former adapted to form a receive beam signal by performing delay control on the digital signals of receive channels corresponding to the at least part of the receiving elements of the ultrasonic receiver, according to a propagation time from a focal point position (21, 212, 213) of the receive beam to the respective receiving element; and an image processor adapted to generate an image using the receive beam signal, characterized in that the receive beam former is adapted to sequentially calculate propagation time values for a plurality of focal points by repeating processing for adding a change of propagation time value corresponding to a change of depth of focal point to an already calculated propagation time value to determine a propagation time value for a next focal point, to execute the repeat processing independently for each of the receive channels, and to calculate the propagation time values in parallel for the at least part of the receive channels, wherein the receive beam former is adapted to determine the change of propagation time value by the change of depth of focal point and recurrence parameters including at least a quotient of two sound velocities which recurrence parameters are determined by a recurrence relation according to the change of the depth of focal point. an ultrasonic receiver having a plurality of receiving elements (200-203, 312-314) for receiving ultrasonic waves reflected or generated inside a subject to generate a respective signal; a sampling means adapted to sample the respective signal received by at least a part of the receiving elements by a cycle of a clock to generate respective digital signals; a receive beam former adapted to form a receive beam signal by performing delay control on the digital signals of receive channels corresponding to the at least part of the receiving elements of the ultrasonic receiver, according to a propagation time from a focal point position (21, 212, 213) of the receive beam to the respective receiving element; and an image processor adapted to generate an image using the receive beam signal, characterized in that the receive beam former is adapted to sequentially calculate propagation time values for a plurality of focal points by repeating processing for adding a change of propagation time value corresponding to a change of depth of focal point to an already calculated propagation time value to determine a propagation time value for a next focal point, to execute the repeat processing independently for each of the receive channels, and to calculate the propagation time values in parallel for the at least part of the receive channels, wherein the receive beam former is adapted to determine the change of propagation time value by the change of depth of focal point and recurrence parameters including at least a quotient of two sound velocities which recurrence parameters are determined by a recurrence relation according to the change of the depth of focal point.