To provide a drain piping structure which can prevent the flame and smoke of a fire breaking out on a lower floor from reaching an upper floor, even if a combustible resin pipe is used as a standpipe installed on the upper floor of a floor slab.

This drain piping structure 1 comprises a metal through-standpipe joint 2 which is fixed through the floor slab 9 in a building, and a bend pipe 7 which is positioned below the through-standpipe joint. The through-standpipe joint and the bend pipe are connected to each other via a connecting pipe 6 which is formed of a combustible material. A thermally-expansible fire-resisting material 3 which is molded in a cylindrical shape is provided in a connecting portion between the through-standpipe joint and the connecting pipe or in a portion immediately near it in such a manner that its outer periphery is coated with a metal incombustible member. When a temperature of a thermally-expansible fire-resisting material reaches a predetermined temperature or higher, it is expanded inward to close an inflow passage to the through-standpipe joint from the connecting portion or the portion immediately near it or to reduce a channel area of the inflow passage.