To provide a fire spread preventing device for reducing ceiling work during piping construction.

The fire spread preventing device includes: a drain collecting pipe 2 disposed passing through a slab 7, and having at least an outer layer being fire-resistant; a flammable resin rising pipe 4b with a lower socket externally fitted at its upper part to a joint part 14 of the lower part of the drain collecting pipe 2 and extended and protruded downward; a nonflammable case member 19 covering the outer periphery of the upper part of the rising pipe 4b with the lower socket so as to include the lower part of the drain collecting pipe 2; and a thermally expansive member 20 disposed downward of the lower end of the drain collecting pipe 2 between the inner peripheral face of the case member 19 and the outer peripheral face of the upper part of the rising pipe 4b with the lower socket. A mounting ring 33 is externally fitted and mounted onto the outer surface of the drain collecting pipe 2, and the case member 19 is connected to the mounting ring 33 via connecting means 34 in a suspended fashion.