To provide a cooling device having a simple configuration, capable of cooling a space effectively and preventing inclusion of dust etc. in the space to be cooled.

A corrugated fin 6 in which a plurality of mountain portions 4 and valley portions 5 are continuously folded back to form a corrugated plate face 16 is installed in a partition wall part between an inner space 12 where a heat source is arranged and an outer space 13 in a form of partitioning the outer space 13 and the inner space 12. The plate face 16 is formed slantly so that the plate face 16 forming the mountain portions 4 on both sides is opened relative to the valley portion 5. Air passages 14, 15 surrounded by the mountain portions 4 and the valley portions 5 of the fin 6 serve as a wind flowing passage. Gas within the inner space 12 is introduced from the Z direction to the air passage 14 and is made to pass in the Y direction along plate faces 16a, and gas in the outer space 13 is introduced from the Z direction to the air passage 15 and is made to flow in the Y direction along plate faces 16b on the side opposite to the plate faces 16a on the inner gas flowing side of the fin 6.