PURPOSE: To prevent water perfectly from leaking out into an indoor side, even if overhead flooding inundation is generated on the connected section of a roof sheathing or the like.

CONSTITUTION: The side edge sections 5b, 5b of the face plate sections 5a of leakage-water-proof plates 5 are engaged to be respectively inserted into left and right channel sections 21, 21 opening to the upper sides of the rafters 2 of W-shaped cross-sectional areas. The outer peripheral surfaces of the lower sections of the rafters 2 are covered with rain-water gutter members 10. Then, even if partial water on the leakage-water-proof plates, infiltrated from the connected sections of roof materials is dropped into the rafters, the water is received by the rain-water gutter members and is led to eaves sides and is discharged from the eaves sides and is not led to sections between the rafters and interior material upper-sections, and then, even if overhead flooding inundation is generated on the connected sections of the roof materials, water can be perfectly prevented from leaking out into an indoor side.