PURPOSE: To perfectly operate the title heat sink even when a pin-fin group is brought up to the prescribed height by a method wherein a sufficient working liquid evaporating area and a sufficient heat-radiating area are given to a meandering fine tube heat bump.

CONSTITUTION: The heat-receiving part H of an I-type pin fin group 3 is formed in such a manner that it has sufficiently long heat-receiving part corresponding to the height of the I-type pin fin group 3. The pair of quantity-of-heat transferring metal flat plates 2-1 and 2-2 of an auxiliary quantity-of-heat transferring flat plate 2 firmly support the I-type pin fin group 3, they support the I-type pin fin group 3 vertical to the heat radiating surface 1-2 of the main quantity-of- heat transferring flat plate 1, and they constitute a frog-shaped fins. Also, the main quantity-of-heat transferring flat plate 1 firmly and vertically supports the heat-radiating unit, composed of the auxiliary quantity-of-heat transferring flat plate 2 and the I-type pin-fin group 3, using strip grooves 1-3 provided on the heat-radiating surface 1-2. As a result, the I-type pin fin group 3 can be operated actively even the height of the pin fins is several hundred millimeters or higher.