To provide a water cut-off rubber fastening device for an arrival portal facility for enabling an excavator or a propulsion pipe propelled and buried from the underground to safely arrive in propulsion work.

The water cut-off rubber fastening device is formed from: an annular pressing material 10 which is worked in an arcuate shape correspondingly to an outer diameter of a propulsion pipe divided into at least two or more pieces and disposed so as to overlap both end portions for a predetermined length while covering a full circumference of an excavator 1; an elastic metal fitting which is fixed on both end portions of the divided annular pressing material 10 in such a manner that convex-shaped flanges oppose each other; and fastening means 9 which fastens the flanges of support materials in a movable manner. In the water cut-off rubber fastening device, the annular pressing material 10 is provided in an annular shape so as to cover the full circumference of the excavator 1 from an upper side of a water cut-off rubber 4 in the state where the excavator 1 protrudes from an insertion hole of the water cut-off rubber 4 of an arrival portal facility 2 to an arrival side, and narrowed down by the fastening means 9 fastened to the support materials in end portions of the annular pressing material 10, thereby uniformly adhering the excavator 1 and the full circumference of the water cut-off rubber 4.