PURPOSE: To prevent a swaying during the time of gripping a fuel assembly and to shorten the time of exchanging fuel assemblies by providing a collar to a mast in order to support sideways the fuel assembly lifted by a fuel gripper.

CONSTITUTION: A fuel assembly 8 is lifted by a fuel gripper 3 at a handle 3 and a side surface of the fuel assembly 8a is horizontally supported by a spacer 18 of a collar 9. By being supported at two vertical positions in this way, a swaying of the fuel assembly can be prevented. Accordingly, by refuelling with this refuelling machine, a waiting time during which the swaying of the fuel assembly subsides or a time required for a manual adjustment of a mast position, can be much saved.