Heat sinks and heat exchangers according to the present invention are not limited to the configurations of working example 1 to working example 6 described above, and these configurations can be modified as appropriate within a scope that does not depart from the gist of the present invention. For example, working example 1 to working example 5 describe examples in which the fin plates all have the same configuration. However, other configurations may be adopted in which some of the fin plates of the plurality of fin plates have a plate thickness that is thicker than the other fin plates or may differ from the other fin plates in, for example, having unevenness or the like on its surfaces. For example, FIG. 18 shows a modification (heat sink 103′) of the embodiment of FIGS. 9-11 (such that the same reference numbers will be used for the various structural elements), in which the spacing or gap C between adjacent fin plates 203 is narrower than the plate thickness of the fin plates 203 because the width of the positioning protrusions 32 is narrower than the plate thickness of the fin plates 203. As a non-limiting example, the plate thickness of the fin plates 203 may be, e.g., 1 mm and the width of the positioning protrusions may be, e.g., 0.8 mm, although these thickness and widths may be appropriately selected based upon the particular application of the present teachings.