PURPOSE: To obtain an automatic fitting method of the key groove of a sleeve roll and the key provided to a driving side chuck cone which can realize the automatic fitting of the key groove and the key in a method at very low cost.

CONSTITUTION: By fitting a sleeve roll 10 and a driving side chuck cone 20 in the close condition to approach both member relatively, a key 22 is sunk against a spring 23 by a chucked hole 10b, and a motor 21 is driven to rotate the driving side chuck cone 20. When the key 22 is faced to a key groove 10c, it is fitted to the key groove 10c by the energizing force of the spring 23. Then, a thrust is given to a reverse driving side chuck cone 30 so as to carry out the main chucking.