PURPOSE: To machine the inside surface of a hollow shaft whose inside diameter greatly varies in the axial direction, by rotatably supporting rollers on the tips of arms pivoted on a roller supporting and operating pipe.

CONSTITUTION: A device 1 for machining the inside surface of the hollow shaft 4 by the rollers 13, 13 comprises the roller supporting and operating pipe 6 which can be inserted into the hole 5 of the hollow shaft, and a servo mechanism 7 for controlling the pipe 6. The rollers are operated through the pipe. A wedge member 15 is moved back and forth in the axial direction of the pipe 6 so that the tips 11B, 11B of the arms 11 are swung by the slopes 15C, 15C of the wedge member 15. The rollers 13, 13 are thus caused to follow up the inside surface of the hole 5. Since the shaft 4 is rotated on support means centering the hole 5, the rollers do not need to be rotated themselves. Therefore, the construction is simplified and the inside surface of the hollow shaft whose inside diameter greatly varies in the axial direction can be machined by the rollers.