To provide an installing method and its joint filling device installable at a low cost, which are capable of filling a gap made between a through hole made to a deck plate and a pipe inserted to the through hole by using mortar or concrete.

This installing method for piping comprises a through hole forming process at positions where pipes for building equipment are to be installed; a pipe installing process for building equipment for locating pipes to through holes; a process of installing lower joint filling forms installed in a quickly attachable and detachable manner to outer peripheral portions of the piping of building equipment; an installing process for joint filling devices for the piping of building equipment in which joint filling forms bendable to a cylindrical shape at a position above the lower joint filling forms with an elastic member with its lower portion located on a lower joint filling form for the piping for building equipment at an outer peripheral portion of the piping for the building equipment; and a placing method for mortar or concrete between a peripheral joint filling form for the outer peripheral portion and the piping for building equipment.