Abstract: A hydraulic actuating device for a roof part, which is moveable between a closed position and an open position, of a vehicle, in particular of a camper. The device has a first hydraulic actuator and a second hydraulic actuator, which first and second actuators are designed to drive the moveable roof part in a parallel arrangement. The first and second hydraulic actuators each have a housing in which there is a space in which a piston member is accommodated, dividing the space into an opening chamber and a closing chamber, each housing being provided with an opening connection and a closing connection, which are respectively in communication with the opening chamber and the closing chamber, so that when pressurized hydraulic fluid is simultaneously fed to the opening connections of the first and second hydraulic actuators the roof part moves towards the open position, and when pressurized hydraulic fluid is fed to the closing connections the roof part moves towards the closed position.