PURPOSE: To permit the penetration of a steel pile without noise by a simplified oil-pressure machine by a method in which the upper end of an expander consisting of a cylinder and a piston is connected to a steel sheet pile and the lower end of the expander is connected to both the adjacent steel sheet piles.

CONSTITUTION: The upper end of an expander consisting of a cylinder 3 and a piston rod 4 is connected with pins 6 and 7 and a ring 8 to the steel sheet pile 1b of plural steel sheet piles 1a, 1b, and 1c assembled along the side wall of a pit. The lower end of the expander 2 is connected to the steel sheet piles 1a and 1c with wires 9a and 9b and hooks 10. The expander 2 is shrunk and the steel sheet pile 1b from which the expander 2 is hung down is penetrated into the ground.