To provide a method for sealing a space between an circular wall forming an opening part and the end part of a pipe inserted into the opening part.

A gap between an annular wall 30 forming an opening part 32 and the end part 38 of a pipe inserted into the opening part is sealed by this method. A sealing sleeve having a rubber elastic material is arranged between the annular wall and the outer surface of the end part of the pipe. The sealing sleeve is provided with an inner surface and an outer surface, one of which is rather smooth and the other of which is provided with at least one sealing projection. In order to connect the end part of the pipe provided with non-smooth outer surface to the annular wall, the same sealing sleeve is used. When the sealing sleeve is used to connect the end part of the pipe of a rather smooth outer surface, the sealing sleeve is arranged so that it is engaged with the end part of the pipe with its surface provided with at least are sealing projection extending toward periphery faced inward.