To obtain a structure which is kept from breaking even if a large external force is applied thereto, prevents infiltration of rainwater into an attic, and performs ventilation in the attic.

The structure is comprised of a lower member 10 and an upper member 11. The lower member 10 includes a base portion 12 having a U-shaped cross section which opens downward, and a pair of mounting plates 13, 13 each inclining from a lower edge of the base portion 12 along the slope of a roof. The base portion 12 has a connecting plate 16 arranged on an upper bed thereof, which has a plurality of long holes 17 formed therein. The upper member 11 is fitted onto the base portion 12 so as to cover over outer openings of the respective long holes 17. The outer member 11 has roof plates 29 arranged thereon, and has a plurality of exhaust passages 39, 39 under the roof plates 29, for communicating with the outside. The exhaust passages also communicate with the long holes 17. Further, the upper member 11 has a pair of retaining members 25, 25 fixed thereto, which function to retain upper surfaces of tiles 20, 20 arranged on the respective mounting plates 13, 13.