PURPOSE: To automatically fit a bearing on a shaft without necessitating exact control of keyway position at the time of placing a roll by controlling a rolling roll in a prescribed rotational position by holding dihedral width parts for rotationally driving the rolling roll between two prescribed parallel planes and pressing by a roll rotational position controlling means.

CONSTITUTION: The traversing tables 61 of two-way traveling trucks 65 are advanced, stopped and, by elevating a lowered chock 62, being in contact with a chock 52, a supporting state is made. The keyway position control is executed by operating the roll rotational position controlling means 63 on a side where dihedral width parts 54 of the roll 51 are present so that two planes 89a, 89b are approached each other and a clamper 1 is made in unclamped state by operating clamper manipulating parts 64 of two-way traveling trucks 65 so that pushrods 94a, 94b are projected. When traversing tables 61 are respectively retreated in this state, the tables are retreated with the chocks supported, so the chock 52 is slipped out of the shaft 53.