PURPOSE: To prevent a pile jacking machine from being inclined by installing a repulsion cylinder to a mast and detecting the pressure and the flow rate of a jacking cylinder and operating the repulsion cylinder so as to make up an insufficient reaction in case when the detected value exceeds a reaction value preliminarily input into an arithmetic operation device.

CONSTITUTION: A repulsion cylinder 12 is installed to a mast 4 of a pile jacking and pulling out machine which are continuously installed to sheet piles P. The pressure and flow rate of a pulse fluid pressure cylinder 11 are detected and the detected value is input into an arithmetic operation device while the detected value is compared with a preliminarily input reaction value. In case when the detected value exceeds a setting value, the repulsion cylinder 12 is operated, thereby making for the shortage of reaction force and preventing the pile jacking and pulling out machine from being inclined. This construction makes is possible to jack in the piles vertically no matter how hard the ground may be.