To provide a spacer for a lock bolt which is intended for the lock bolt whose screw node line is divided by two smooth stretching sections facing each other across the center of axle on a peripheral surface along the longitudinal direction, installable from the side surface of the lock bolt, stable when installed and easy in use by a small operating force.

The spacer 1 for the lock bolt is formed by integrating a spring steel sheet and composed of four interval holding pieces 4a-4d and cylindrical parts 2,3 of substantially elliptical cross sections provided on their both sides. Each cylindrical part 2,3 has an opening which continues to ends on both sides where a pair of turn-back parts are formed. When mounting, the turn-back parts are applied to the screw node line 12 of the lock bolt 10 and pushed into from the rear, so that openings are further opened to get over a smooth section 11 and that the lock bolt 10 is fitted into the cylindrical part 2,3 at both the ends.