PROBLEM TO BE SOLVED: To provide a water cut-off structure and a refilling method of a backfill material capable of improving the cut-off performance, the removability, and the safety of a check valve, and the safety and the workability during refilling of the backfill material in the water cut-off structure with the check valve provided for a backfill material filling hole of an earth/water pressure resistant structure such as a shield segment.SOLUTION: A filling pipe 2 is provided with a first check valve (a simple check valve 20) which is normally closed and opened with the filling pressure of the backfill material, on the internal backfill material packing side (the natural ground side), and a backfill material filling hole is provided with a removal, second check valve (a high cut-off check valve 10) which is normally closed and opened with the filling pressure of the backfill material, on the internal backfill material filling side (the side of the internal space of a segment ring). The backfill material filling hole of the segment is cut off with the double check valve, the cut-off performance and the safety are improved, and the safety and the workability during refilling the backfill material are improved.