A closure device for the vacuum-tight closure of an opening includes a closure element, at least one rod that projects out of a housing of the closure device and that, outside the housing, supports the closure element and that is rigidly connected to a carrier piece, a transmission unit which is adjustable by a drive parallel to the longitudinal adjustment direction between an initial, open position of the closure element, a middle position, in which the closure element assumes the intermediate position, and a closed, end position. At least one spring is arranged between the transmission unit on the carrier piece, and a stop device which, during adjustment of the transmission unit from the middle to the end position, blocks a further adjustment of the carrier piece parallel to the longitudinal adjustment direction. The transmission unit is guided by at least one longitudinal linear guide to be displaceable relative to the housing parallel to a longitudinal adjustment direction, and the carrier piece is guided by at least one oblique linear guide to be displaceable relative to the transmission unit parallel to an oblique adjustment direction.