In a cooling device for cooling an object to be cooled without using a forced cold air circulating system, which circulates cold air forcibly, a cooling device at a practical level is provided, and a cooling device capable of achieving a sufficient cooling effect is provided. A cooler 18 is provided in an interior that is insulated adiabatically from an exterior, a cooling fan 20 is disposed on a front surface of the cooler 18, a cooling chamber 22 in which an object to be cooled is placed is defined by a space in front of the cooling fan 20, a cooled air behind the cooling fan 20 is drawn with the fan and allowed to flow into the cooling chamber 22, and a/D=½ to ¼ is satisfied, where a indicates a dimension of a gap between the cooler 18 and the cooling fan 20 along a front-back direction and D indicates a diameter of the cooling fan 20.