An ultrasonic inspection apparatus comprising an ultrasonic array probe having a plurality of ultrasonic elements arranged at predetermined positions for transmitting ultrasonic waves to a test object and receiving ultrasonic waves reflected by a test object; wherein the ultrasonic inspection apparatus comprises: a test object information acquiring section for acquiring information on the test object; an input unit for receiving the inputs from the outside and also from the test object information acquiring section; an estimated shape-reflected-wave arrival time calculator for computing estimated shape reflected wave arrival time of each of estimated shape reflected waves on basis of estimated sound velocity in the test object, the estimated shape reflected wave arrival time being estimated time for the estimated shape reflected wave to arrive at the ultrasonic element when the ultrasonic wave is reflected at a shape-indicating reflection part thereof; an actual shape-reflected-wave arrival time extractor for extracting actual shape reflected wave arrival time on basis of an actual shape reflected wave transmitted from the ultrasonic element used for ultrasonic wave transmission, propagated through the test object, reflected by the shape-indicating reflection part and received by each of the ultrasonic elements used for receiving the ultrasonic wave; a shape-reflected-waves time difference calculator for computing difference obtained by subtracting the actual shape reflected wave arrival time from the estimated shape reflected wave arrival time as shape reflected waves time difference; a delay time calculator for computing estimated delay times and delay times, wherein the estimated delay times are set so that the ultrasonic waves are made to converge to focus by using the plurality of ultrasonic elements when the estimated sound velocity in the test object is assumed to be constant, the delay time calculator computing each of delay times after executing a corrective action of adding or subtracting the shape reflected waves time difference to or from the estimated delay times; and a synthesizing calculator for computationally determining a synthetic waveform of the waves using the delay times for respectively shifting corresponding timing of ultrasonic wave transmission and reception received by the ultrasonic elements, characterized in that the shape-indicating reflection part is a part of the test object that relates to the overall shape of the test object or a representative part of the test object in terms of the shape and that differs from a flaw to be detected in the test object. a test object information acquiring section for acquiring information on the test object; an input unit for receiving the inputs from the outside and also from the test object information acquiring section; an estimated shape-reflected-wave arrival time calculator for computing estimated shape reflected wave arrival time of each of estimated shape reflected waves on basis of estimated sound velocity in the test object, the estimated shape reflected wave arrival time being estimated time for the estimated shape reflected wave to arrive at the ultrasonic element when the ultrasonic wave is reflected at a shape-indicating reflection part thereof; an actual shape-reflected-wave arrival time extractor for extracting actual shape reflected wave arrival time on basis of an actual shape reflected wave transmitted from the ultrasonic element used for ultrasonic wave transmission, propagated through the test object, reflected by the shape-indicating reflection part and received by each of the ultrasonic elements used for receiving the ultrasonic wave; a shape-reflected-waves time difference calculator for computing difference obtained by subtracting the actual shape reflected wave arrival time from the estimated shape reflected wave arrival time as shape reflected waves time difference; a delay time calculator for computing estimated delay times and delay times, wherein the estimated delay times are set so that the ultrasonic waves are made to converge to focus by using the plurality of ultrasonic elements when the estimated sound velocity in the test object is assumed to be constant, the delay time calculator computing each of delay times after executing a corrective action of adding or subtracting the shape reflected waves time difference to or from the estimated delay times; and a synthesizing calculator for computationally determining a synthetic waveform of the waves using the delay times for respectively shifting corresponding timing of ultrasonic wave transmission and reception received by the ultrasonic elements, characterized in that the shape-indicating reflection part is a part of the test object that relates to the overall shape of the test object or a representative part of the test object in terms of the shape and that differs from a flaw to be detected in the test object.