To surely keep a fireproof-waterproof condition of a joint part of fireproof-waterproof members in a building for a long time and to eliminate unevenness of a floor plate surface without using any unevenness regulating member so as to accomplish reduction in construction costs and part costs.

A joint main body 2, in which a projection part 4 is formed in the center, and stress absorbing water cut-off members 3 stuck in both side ends of the joint main body 2 are arranged between a floor plate 6 made of fireproof-waterproof material and a floor 7 of a supporting body, and the projection part 4 in the joint main body 2 is positioned in a joint part 12, while the floor plate 6 is supported by means of the stress absorbing water cut-off members 3, and the whole of a joint structure body 1 is fixed on the floor 7 side. In this way, the joint part 12 is sealed by means of the stress absorbing water cut-off members 3, while a fireproof property is provided by means of the metallic joint main body 2.