PURPOSE: To enable the sufficient execution of a flaw detection test by a UT (ultrasonic test) and the improvement of maintainability by forming a bucket wheel into the structure divided into a disc part and a bucket part.

CONSTITUTION: A bucket wheel 41 is formed of an integrally cast divided bucket 42 and a disc part 43, and the divided bucket 42 and disc part 43 are fastened by several reamer bolts 44 and nuts 45. The face for disposing vertical probes 47 and oblique probes 48 can be thereby secured sufficiently. Accordingly, a flaw detecting test can be performed sufficiently to improve maintainability. Furthermore, since assembling and fixture can be simply performed using only a few reamer bolts 44 and nuts 45, high quality and low cost can be attained effectively.