PURPOSE: To prevent damage of a flexible cut-off member during and after driving, by a method wherein a pair of laminar parts are intercoupled by means of the flexible cut-off member to form the joint of a steel sheet pile, and a protecting plate part, covering the flexible cut-off member, is provided in series connection to the one side of the laminar part.

CONSTITUTION: Fastening parts 2b and 2b' are attached to a pair of laminar parts 2 and 2' having joint parts 2a and 2b for connection of adjoining steel sheet piles with each other. A flexible cut-off member 1 made of rubber is extended between the fastening parts 2b and 2b' and are secured by means of bolt nuts 3 and 4 to form a joint A for the steel sheet pile. Further, thin sheets 5b and 5b' are welded to base parts 5a and 5a' of the one planar part 2 to form protecting plate parts 5 and 5'. This, since the thin sheets 5b and 5b' are not secured to the other planar part 2' prevents disturbance of deformation yielding as the joint, and enables the flexible cut-off member 1 from being damaged.