PURPOSE: To perform the flaw inspection of a component to be inspected in a short time by inspecting only a component which has a defect while fractionizing the overall height of a weld zone into an upper, an intermediate, and a lower part or more.

CONSTITUTION: The component 1 to be inspected which is formed by welding the joined part of a cylindrical metallic component along the circumference is placed on a jig 2 and flaw detection is started. Then, an inspected component memory 17 outputs the stored size of the component 1 to a Y-axial controller and an X-axial controller 19 so as to determine the height and right-left position of a probe 3 so that the ultrasonic wave beam of the probe 3 strikes on the weld zone of the component 1 to overall height. The controllers 21 and 19 position a Y-axial mechanism part 9 and an X-axial mechanism part 10 and then send their outputs to a table rotation controller 23 to make one turn of a table 4, thereby performing flaw detection to the entire circumference of the weld zone. If a defect is detected, the mechanism part 10 is moved away from the weld zone and the mechanism part 9 is moved in the order of the upper, intermediate, and lower parts to detect a defect position. Thus, the flaw detection is carried out in a short time.