A ventilation device may include first and second supply ducts, a mixing section having a mixing duct into which the first and second supply ducts may lead, the first and second supply ducts arranged in the mixing section adjacent one another in a transverse direction, and first and second guides in the mixing section each running in the transverse direction and being located opposite one another in a longitudinal direction running transversely to the transverse direction, each guide having two guide walls running in the transverse direction and located opposite one another in a height direction running transversely to the transverse direction and longitudinal direction, at least one of the guide walls sloping away from the other guide wall at a slope angle with respect to the longitudinal direction. A valve may have a plate body and may be adjustably guided with a first guide section running in the transverse direction in the first guide and with a second guide section running in the transverse direction in the second guide. An actuator may during operation adjust the valve in the transverse direction between a first position, in which the valve fluidically separates the second supply duct from the mixing duct and opens a fluidic connection between the first supply duct and the mixing duct, and a second position, in which the valve fluidically separates the first supply duct from the mixing duct and opens a fluidic connection between the second supply duct and the mixing duct, wherein the first guide section has a first thickness running in the height direction and which is smaller than a second thickness of the second guide section running in the height direction in such a manner that both guide sections are each in contact with both guide walls of the associated guide.