To provide a waste water collecting joint, light-weighted, and having excellent fire resisting performance and workability of work.

This waste water collecting joint includes: a body part having upper and lower vertical pipe connecting parts to which a waste water riser is connected and a slab penetrating part disposed to penetrate a floor slab; and at least one lateral branch pipe connecting part provided to communicate to the upside of the slab penetrating part of the body part, wherein at least the communicating part of the lateral branch pipe connecting part of the body part is shaped like a cylinder having a larger diameter than the inside diameter of the waste water riser, and provided with a tapered cylinder part gradually decreased in diameter as it goes toward the lower side to have the substantially same inside diameter as that of the waste water rise connected to the lower side of the large-diameter cylindrical part. The waste water collecting joint is formed by assembling a plurality of joint component members, and among the plurality of joint component members, at least the joint component member constituting the slab penetrating part is formed of a fire resisting thermal expansion resin pipe having a fire resisting expansive layer made tubular using fire resisting expansive resin composition.