Abstract: A cooling system for cooling electronic circuit components mounted on a wiring substrate includes containers placed on the respective components, and nozzles each having a central through-hole and peripheral through-holes. The outer bottom surface of each container is in good thermal contact with a corresponding electronic circuit component. Each nozzle is inserted into a corresponding container so that first ends of the central and peripheral through-holes of the nozzle are positioned within the container, while the opposite ends are positioned outside the container. The gap between the inner side wall of each container and the outer side surface of a nozzle inserted into the container is hermetically sealed by a sealing member. Liquid coolant is supplied through the central through-hole of each container into the container and then discharged through the peripheral through-holes to a location outside the container.