To provide a structure for completely discharging the air of an attic to the outside in a short period of time.

Plain ridge rows 11 and 11a in which bar plain ridge tiles 1 are arranged in parallel and fixed in the longitudinal direction of a plain ridge tile fixing member 9 mounted on a plurality of support materials 8 installed on a ridge part A are formed in a plurality of stages in a vertical direction on both side surfaces of the plain ridge tile fixing member 9, and a clearance 12 is formed between the adjacent plain ridge rows 11 and 11a, and a side panel between the plain ridge row 11 in a first stage and a pantile T in a roofing state just under that is closed, and a ventiduct 13 is formed between the plain ridge row 11 and the plain ridge tile fixing member 9 with a groove 7 in a whole vertical direction formed on the abutment surface of the bar plain ridge tile 1 to the plain ridge tile fixing member 9. Air from the attic is made to pass through the ventiduct 13 in the plain ridge row 11 in the lowermost stage, and to flow in a gap between the adjacent plain ridge rows 11 and 11a, and to flow out of the clearance 12 to the outside.