PURPOSE: To easily connect a water sealing film by mounting a zipper to the adjacent end edges of both a preceding water sealing film and a succeeding water sealing film and then pulling in a rope member connected to a closing member of the zipper.

CONSTITUTION: A preceding water sealing film 1a is installed in a thin groove 3. A setting material 6 is filled up in a thin groove 3 segmented by closing the front sides of branch films 11 and 12 of the water sealing film 1a with a packer 4 so as to solidify muddy water. A pull-in rope is installed rotatively between an anchor buried in the bottom of the thin groove 3 and a sheave on the ground side. Then, both the lower ends of a succeeding water sealing film 1b is connected to each rope and each rope is rotated on the ground side so that each rope may be pulled into muddy water in the thin groove 3. A zipper 2 is mounted to the upper parts of the mutually opposed branch films 11 and 12 of the dead water films 1a and 1b. Moreover, after the rope is mounted to a closing member of the zipper 2, the rope is operated so that the zipper may be closed, thereby connecting the water sealing film 1a to the water sealing film 1b. Furthermore, the setting material 5 is filled up in the thin groove 3 so as to solidify the muddy water.