PROBLEM TO BE SOLVED: To provide a ventilation structure in a wall body structure part of a dwelling house, enabling smooth aeration, improving ventilation performance, and eliminating problems on design, durability, and waterproofness.SOLUTION: In a ventilation structure in a wall body structure part of a dwelling house: sidings 4, 5 are stretched on both of inside and outside of a wall body 1 respectively with ventilation gaps 2, 3 held therebetween respectively; a top board 6 is installed above the wall body 1 with a communication gap 13 secured therebetween; an upper end of the inside ventilation gap 2 and an upper end of the outside ventilation gap 3 are made communicatable via the communication gap 13; an aerator 15 is arranged between the upper face of the wall body 1 and the top board 6 so as to block at least one of the outside and inside ventilation gaps 2, 3; and an opening end face of the aerator 15 is shielded by a vertical face 7a of a cover 7 installed on the top board 6. The aerator 15 can per
