Abstract: A cyclic circuit (20) is constructed by sequentially connecting an expander (22), a heat exchanger (30) and a compressor (21). A dehumidifying mechanism (60) is provided for dehumidifying a heat-absorbing air taken in through an inlet duct (23). An internal heat exchanger (15) is provided for cooling the dehumidified heat-absorbing air and then supplying it to the expander (22). The heat-absorbing air expands in the expander (22) to reduce its temperature. Since the heat-absorbing air has been dehumidified in advance, the moisture thereof does not condense during the expansion thereof. The heat-absorbing air having reached a low temperature through expansion flows into the heat exchanger (30) and absorbs heat from a room air therein. Thereafter, the heat-absorbing air is compressed in the compressor (21), regenerates a rotor member (61) and is then discharged.