To provide a joint for a fire limit penetration part, having a thermal expansion member convenient and easy to handle and construct, and quickly and surely shutting off a penetration part to prevent upward spreading of a fire.

The joint for the fire limit penetration part is disposed in the penetration part of a conduit vertically bored in the fire limit A of the floor, ceiling, or the like of a building, and has a connection end 15 of socket shape below to fit and connect a vertical pipe formed of a conduit member made of a thermoplastic synthetic resin material. The connection end 15 is provided with a metallic expansion holding part 40 of ring-like groove shape with a groove opened toward the vertical pipe, and the fireproof thermal expansion member 45 expanded with the heat of the fire is stored in the ring-like groove shape. The metallic expansion holding part is disposed at the connection end 15 in a state of projecting to the indoor side below the surface of the fire limit, and the thermal expansion member is provided directly facing the peripheral surface of the vertical pipe.