The cooling unit includes: an opening part through which the cooling media flow in； a first flow path； a second flow path； a first heat generation section； a second heat generation section； a first heat dissipation section that is thermally connected to the first heat generation section, and is disposed in the first flow path； and a second heat dissipation section that is thermally connected to the second heat generation section, and is disposed in the second flow path. The second flow path is disposed between the first and second heat generation sections and the first flow path, and the first heat dissipation section has a thermal resistance value smaller than a thermal resistance value of the second heat dissipation section.
