Cooling Device

A cooling device that has a first wide surface and a second wide surface facing the first wide surface, and cools a device to be cooled with a fluid flowing through a flow path that is flat and formed between the first wide surface and the second wide surface, wherein

• the second wide surface has a plurality of protrusion portions protruding into the flow path, the protrusion portions extending in a flow path width direction, the protrusion portions being arranged side by side in a fluid flow direction,
• the first wide surface is not provided with the protrusion portions,
• the protrusion portions each include:
• a first inclined surface inclined to come close to the first wide surface from upstream to downstream in the fluid flow direction;
• and
• a second inclined surface disposed alternately with the first inclined surface in the fluid flow direction and inclined to be distanced from the first wide surface from upstream to downstream in the fluid flow direction, and
• the protrusion portions each are formed such that, in a cross section taken along the fluid flow direction, a virtual first circle is inscribed at three points on the first wide surface, the second inclined surface, and the first inclined surface adjacent to the second inclined surface downstream in the fluid flow direction.