To provide a ventilation structure of a ridge part for urging the ventilation of a space part formed between a roof and the ceiling of a building, without infiltrating rainwater into the space part.

In this ventilation structure 1 of the ridge part, a rafter clearance member 6 has an upper fixing plate 7 for installing the rafter clearance member 6 in a ridge material 3, a side face plate 9 having an air vent 8 penetrating outside from an inside space X, and a lower edge part 10 formed along a surface of a roof tile 5 in a lower end part of the side face plate 9, and has a ventilation member 13 having an under surface part 11 fixed in close contact inside the rafter clearance member 6 and formed along the surface of the roof tile 5 and a ventilation groove 12 formed in a place coming into close contact with the air vent 8 so as to communicate with the air vent 8 from the inside space X, and an elastic airtight member 14 formed along the under surface part 11 of the ventilation member 13 and interposed in close contact between the under surface part 11 and the roof tile 5.