To realize miniaturization without the need of the increase of an area of a heat exchanger by making an air volume per cycle substantially same as that of a general purpose machine by providing two circuits of independent freezing cycles, and disposing an indoor side heat exchanger such that it is arranged in series with respect to a flow of suction air.

A front stage side heat exchanger 4 disposed in an indoor unit 1 of an all fresh type constant temperature-humidity air conditioner is adapted to be operated upon high load operation, and a rear stage side heat exchanger 5 is adapted to be operated upon low load operation. These heat exchangers 4, 5 are disposed in series with respect to a flow of air, and a thermostat 8 is set to be off at a suction temperature where blowoff temperature of the rear stage side heat exchanger 5 becomes 10°C, and when blowoff temperature of the front stage side heat exchanger 4 is less than a set value, a front stage freezing cycle is interrupted. In contrast, there are disposed in an outdoor unit 2 outdoor heat exchangers 10, 11 communicated with the front and rear stage freezing cycles 4, 5, air fans 12, 13, and compressors 14, 15.