<p>High heat generation member (1) of electronic integrated circuit etc. is boiled and cooled. A refrigerant steam is generated by cooling of the heat generation member (1) and is condensed by a condenser (5) which is provided in an upper portion of a container (2). A refrigerant steam flow path (4) and a condensed refrigerant flow path (6) from the condenser (5) are separated with a partition wall (7). The condensed liquid (3) sent back to the partition wall (7) is supplied to the heat generation member (1) through the partition wall (7).</p>
