PURPOSE: To raise the safeness of rising and falling operations of a pile driver by a method in which the gravitational center of the whole of a pile driver is obtained from the rising and falling angles of a leader and the weights, gravitational center positions, and dimensions of each portion of the pile driver and also safety and falling moment at the falling support point are obtained, and the rightness of self-rising and falling is judged and displayed.

CONSTITUTION: A leader 3 is attached to the front of a travelling device 1b in a rising and falling manner and supported by two expandible back stays 5. An angle gauge 11 to detect the rising and falling angle θ of the leader 3 is provided to the front bracket 2, an arithmetic controller 10 is provided in an operator room 1e, and the angle gauge 11 is connected to the controller 10. The arithmetic controller 10 consists of a memory 10b, an arithmetic unit 10a, and a displayer 10c. The gravitational center position of the whole of the driver is calculated from the weight, gravitational center, and dimensions of each part of the pile driver and the rising and falling signals of the leader, the safety and falling moment at the falling support points are compared in the controller 10, and the rightness of self-rising and falling is displayed on a displayer 10c.