A laminated core type heat sink, comprising: a plurality of flat plates , each of the plurality of flat plates being a metal flat plate having a plurality of slits punched out in parallel to each other, and a plurality of long and thin longitudinal ribs in parallel to each other and transverse ribs linking respective adjacent longitudinal ribs , formed between the slits ; and a core in which respective ones of the plurality of flat plates are laminated while the longitudinal rib is matched mutually and a position of the transverse rib is shifted mutually, first and second end lids are arranged at respective ends in a lamination direction, and each of the plurality of flat plates is joined; wherein the laminated core type heat sink is arranged so that a refrigerant can be circulated into each of the slits of the core in a longitudinal rib direction, and an object to be cooled can be joined to an outer surface of the first end lid , wherein the plurality of flat plates in the core includes: a plurality of first plates that each have identical thickness, the plurality of first plates including a first plate that is arranged first in the lamination direction from the first end lid , and a plurality of first plates that are adjacent to each other in a lamination direction, and a second plate that is arranged second in the lamination direction from the first end lid , characterized in that the second plate is thicker than the thickness of each of the plurality of first plates . a plurality of flat plates , each of the plurality of flat plates being a metal flat plate having a plurality of slits punched out in parallel to each other, and a plurality of long and thin longitudinal ribs in parallel to each other and transverse ribs linking respective adjacent longitudinal ribs , formed between the slits ; and a core in which respective ones of the plurality of flat plates are laminated while the longitudinal rib is matched mutually and a position of the transverse rib is shifted mutually, first and second end lids are arranged at respective ends in a lamination direction, and each of the plurality of flat plates is joined; wherein the laminated core type heat sink is arranged so that a refrigerant can be circulated into each of the slits of the core in a longitudinal rib direction, and an object to be cooled can be joined to an outer surface of the first end lid , wherein the plurality of flat plates in the core includes: a plurality of first plates that each have identical thickness, the plurality of first plates including a first plate that is arranged first in the lamination direction from the first end lid , and a plurality of first plates that are adjacent to each other in a lamination direction, and a second plate that is arranged second in the lamination direction from the first end lid , characterized in that the second plate is thicker than the thickness of each of the plurality of first plates . a plurality of first plates that each have identical thickness, the plurality of first plates including a first plate that is arranged first in the lamination direction from the first end lid , and a plurality of first plates that are adjacent to each other in a lamination direction, and a second plate that is arranged second in the lamination direction from the first end lid , characterized in that the second plate is thicker than the thickness of each of the plurality of first plates . <EOS>