A process and tool for producing a composite body part for a motor vehicle, especially for producing a roof module, the tool having a first tool part and a second tool part which are movable relative to one another. The outer skin is inserted in the first tool part, at least part of the peripheral edge area of the side of the outer skin facing the first tool part being moved into sealing contact with a seal arrangement which is provided on the first tool part, plastic material is applied to the side of the outer skin facing away from the first tool part, the second tool part provision shaping the plastic material, and the composite body part being released from the seal arrangement and removed from the tool.