PURPOSE: To efficiently remove attached foreign matters by a method wherein a rope having irregularities on its surface is turned up and parallelly stretched over the outer surface of a movable form (form for tunnel lining) for use in lining of tunnel and the rope is caused to rotate on its axis, while being moved back and forth.

CONSTITUTION: When lining concrete is placed on the inner wall of a tunnel, a rope 3 around which a plurality of strands having different diameters are helically wrapped to form a large number of recesses and protrusions is stretched over the outer surface 2 of a form for tunnel lining 1 so as to be turned up and wrapped around the surface 2. A hydraulic cylinder 5 is provided at the end of the rope 3 to generate tension and to move the rope back and forth along the outer surface 2, rotating further the rope 3 on its own axis. And foreign matters such as blocks of concrete adhered to the outer surface of the form 1 are scraped off by the rope 3. As a result, foreign matters are completely removed and unsymmetrical wear of the rope can be eliminated, resulting in improved durability.