PURPOSE: To reduce dangerousness that an HC refrigerant catches fire, by setting a compressor in a machine chamber provided at an upper part on a rear face of a heat insulation casing and setting a duct for diffusion/heat. radiation above the compressor, a duct for diffusion in the machine chamber and a fan at the bottom of the machine chamber.

CONSTITUTION: Air in a machine chamber 7 provided at an upper part on a rear face of a heat insulation casing 2 is forcibly discharged at all times from the upper part of the machine chamber 7 by an air force of a fan 19 through a duct 18 for diffusion/heat radiation and a duct 21 for diffusion. In this case, even in the case where a combustible HC refrigerant 14 leaks into the machine chamber 7 through a hole bored in a welded part due to welding failure or corrosion at a welded part between a compressor 9 and a discharge pipe 10, or between the compressor 9 and a suction pipe 13, the HC refrigerant 14 is forcibly discharged and diffused by the fan 19 together with air in the machine chamber 7 through the duct 18 for diffusion/heat radiation and the duct 21 for diffusion. Accordingly, the HC refrigerant 14 is diffused in ambient air without being stayed at the lower part of the heat insulating casing 2, and the possibility of catching fire due to an electric contact is minimized.