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.