To provide a hole machining tool which eliminates such a bother as to measure an inner diameter of a circular hole 7 formed in a workpiece 6 whenever the hole is formed, to thereby reduce costs required for finishing the circular hole.

The workpiece 6 has a prepared hole formed therein beforehand, and an inner peripheral surface thereof is ground by a grindstone 2 to form the circular hole 7 having the predetermined inner diameter. Then a rod portion 3 supporting the grinding bar 2 is sheathed with a radial needle bearing 4 in an axially movable manner, and the radial needle bearing 4 is pressed to the grinding bar 2 via a sleeve 13. The outer diameter of an outer ring 12 of the radial needle bearing 4 is set to a lower limit value of an allowable dimension of the circular hole 7. When the grindstone 2 is worn and the inner diameter of the circular hole 7 becomes smaller, the outer ring 12 cannot enter the interior of the circular hole 7, and therefore a displacement sensor 5 detects the fact, which notifies the operator that the hole machining tool 1 should be exchanged.