In a closing machine (1), an inner diameter chuck (8) that grips an inner peripheral surface of a work piece (9), a work piece (9) introducing device that moves the inner diameter chuck (8) in a Y axis direction of the work piece (9), and an introduction stopper (12) that projects onto an introduction path of the work piece (9) are used in such a manner that the inner diameter chuck (8) grips the inner peripheral surface of the work piece (9) while the work piece (9) abuts against the introduction stopper (12), the introduction stopper (12) is removed from the introduction path of the work piece (9), and the work piece (9) is introduced into an outer diameter chuck (7) by moving the inner diameter chuck (8) in the Y axis direction of the work piece (9).