A cooling device includes a base, first and second heat generating parts connected to the base, first and second passages formed in the base and a partition wall disposed in the base. Liquid refrigerant flows through the first and the second passages for cooling the first and the second heat generating parts, respectively. The first and the second passages are stacked one above the other through the partition wall in the base. The partition wall includes a first region opened to allow liquid refrigerant in the first passage to flow into the second passage and a second region located on the side of the first region to allow liquid refrigerant in the first passage to flow toward the downstream end of the first passage. The first region is formed such that an opening area of the first region is greater than an opening area of the first passage.