A ventilation structure (1a) includes a housing (10a) and a ventilation component (20a). The housing (10a) has a first surface (12) defining a lateral surface of a columnar space (11c) in an attachment hole (11). The ventilation component (20a) is attached to the housing (10a) to close the attachment hole (11). The ventilation component (20a) has a ventilation path (21) between an inner space (15u) of the housing (10a) and an outer space (15s) of the housing (10a). The ventilation component (20a) includes a supporting portion (23), a gas-permeable membrane (22), a protruding portion (24), and a sealing member (25). The supporting portion (23) surrounds the ventilation path (21) in plan view. The protruding portion (24) protrudes from the supporting portion (23) toward the inner space (15u) of the housing (10a), and is inserted into the attachment hole (11). The sealing member (25) is disposed on an outer periphery of the protruding portion (24), and seals a gap between the first surface (12) and the protruding portion (24).