To obtain a roof structure preventing water leakage without sacrificing the working area of main roofing members by fixing a panel in which the main roofing material, a backing material, and a moisture-permeable waterproof material are integrally constituted, to metallic rafters with a trough-shaped section.

A main roofing member 11 is connected to a backing material and a moisture-permeable waterproof material is provided under the backing material to form a panel. Metallic rafters 21 having a trough-shaped section are fixed to a roof face to be executed at a pitch at which the superposing parts in the direction of the drainage slope of the panels are mutually superposed. Then, the panels are placed on the roofing face and fixed to the metallic rafters 21 with screws 22 having a packing or the like. And hence, the metallic rafter 21 brings out the same function with a gutter and even when water leaks from the superposed parts, the water is prevented from penetrating in the substrate. Accordingly, it is not necessary to uselessly increase the superposing width of the main roofing members 11 and a roof structure preventing water leakage can be obtained.