To provide the structure of a water proof floor that can easily perform waterproofing between adjacent floor panels and acquire the excellent design of a floor face when arranging the floor panels with waterproof sheets previously stuck to the surfaces of floor panel bodies, in parallel to constitute the waterproof floor.

In this structure of the waterproof floor 1 constituted by arranging the floor panels 11 provided with the floor panel bodies 31 and waterproof sheets 51 stuck to the surfaces in parallel to form a continuous drainage slope in a drainage direction D from upstream to downstream, the floor panels 11 adjacent to the drainage direction D are connected holding a connecting floor panel 21 between them, and the thickness 41T of a connecting floor panel body 41 constituting the skeleton of the connecting floor panel 21 is set to the dimension (31T-51T) obtained by subtracting the thickness 51T of the waterproof sheet 51 from the thickness 31T of the floor panel body 31. The waterproof sheet 51 stuck to the surface of the floor panel body 31 is extended onto the connecting floor panel 21 side from the end part of the floor panel body 31.