A cooling device for cooling an electronic component (semiconductor module) includes a cooling tube adapted to be disposed in contact with the electronic component and having an internal coolant flow channel for the passage therethrough of a cooling medium, and a high-pressure tube disposed adjacent to a surface of the cooling tube that faces away from the electronic component, the high-pressure tube having a hollow interior that can be filled with a high-pressure fluid having a pressure higher than that of the cooling medium. An electric power conversion device comprised of a plurality of semiconductor modules and the cooling device as means for cooling the semiconductor modules is also disclosed.