PURPOSE: To obtain a noise-reducing effect and contrive a smaller overall device size by providing an air duct between a partition plate, which is disposed in a cabinet so mounted that a blowing port and a blow-off port of a fan casing are connected to each other, and a heat exchanger.

CONSTITUTION: A fan casing 21 with a fan 2 contained therein is mounted on a partition plate 3, and is contained in a cabinet 1 in that condition. The partition plate 3 is provided with a blowing port 31 for passing therethrough an air flow from the fan 2. An air duct 5 is provided between the partition plate 3 and a heat exchanger 4 in such a shape that the opening area thereof is increased toward the outer side and generation of Karman's vortex is suppressed, whereby the air flow through the blowing port 31 is supplied through the duct 5 to the heat exchanger 4. The duct 5 is so designed that protrusion lengths A and B at upper and lower parts of the blowing port are in the ratio of about 3:1, the angle C toward the lower side is about 30°, and the opening angle D in the widthwise direction of the blowing port is about 20°, whereby it is possible to reduce noise and contrive an overall compact construction.