A ventilation unit with: a ventilation body that allows gas to circulate between the outside and inside of a housing; a support member that supports the body attached to an opening portion formed in the housing; and a sealing member between the support member and the outer surface around the housing opening portion and seals a gap between the support member and the housing, wherein the unit performs ventilation between the outside and inside of the housing through the body while attached to the opening portion of the housing. The support member includes: an attachment portion to which the sealing member is attached; and a wall portion around the attachment portion, wherein, in a state where the support member is attached between the support member and the housing, a distance between the support member and an external surface in the support member wall portion is 5.0 mm or more.