An assembly device for pressing and/or retracting components into an opening in a housing part and/or for sliding on and/or pulling off components, including a base body and a counterpart, the base body has a reciever for receiving the counterpart, a tube with a contact section, the tube is slid in sections over the base body, and the tube and the base body are displaceable relative to each other by at least one actuator so that the distance is variable between the contact section and the reciever. In a method, a component is arranged in front of one side of an opening, the counterpart is passed from the other side of the opening through the opening and the component, the counterpart is connected to the base body via the reciever, and the distance between the contact section and the reviever is changed by the actuator to press in the bearing.