To provide an apparatus for forming an aperture which apparatus can simply carry out the overall mounting work by satisfactorily securing a space for inserting piping materials, and by satisfactorily enlarging the tilting movement of a back side member with respect to a face side member.

The apparatus for forming the aperture comprises a fixing ring 10 which has an insertion part 15 capable of inserting a piping material, etc. therethrough, and is arranged on the back side of a through hole 2 of a mounting portion 1, a fixing plate 20 which has an insertion part 25 capable of inserting piping material, etc. therethrough, and is arranged on the back side of the through hole 2 of the mounting portion 1, and a connecting member 41 which connects the fixing ring 10 to the fixing plate 20 and is flexible in its longitudinal direction.