Abstract: An ultrasonic flaw detecting apparatus of electronically scanning type comprises a plurality of ultrasonic vibrator elements disposed in an arcuate array, wherein groups of N vibrator elements arrayed in the circumferential direction of an object under test are sequentially changed over to one another on one-by-one base to thereby scan an object under test with ultrasonic beams. By controlling phases of pulse signals applied to the individual vibrator elements, a region of focus of the ultrasonic beams is set at a predetermined depth of the object under test. For reception, only the echoes reflected from a predetermined focal range are selectively extracted by providing corresponding window or gate means.