It is an object to provide a cooling device for optimally cooling a semiconductor device on a CPU blade which is detachable with respect to an electronic apparatus using the cooling device with compact structure for reducing power consumption. A cooling device for cooling a semiconductor device disposed on an electronic circuit substrate in a casing of an electronic apparatus, comprising a first cooling unit comprising a first heat absorbing portion and a first heat releasing portion, and a second cooling unit comprising a second heat absorbing portion and a second heat releasing portion, wherein the first heat absorbing portion is disposed in contact with the semiconductor device, the second heat absorbing portion is detachably disposed in contact with the first heat releasing portion, a phase-change refrigerant is contained in the first cooling unit, and the second heat releasing portion is disposed outside the casing.