A multi-chamber heat-pump type air conditioner in which a plurality of room units (2, 3, 4) are connected to one heat source unit (1), cooling and heating can be effected selectively for each room unit (2, 3, 4), and cooling can be effected by one room unit and heating can be simultaneously effected by another, wherein the high-level pressure or low-level pressure is controlled from rising high as compared to the time of normal operation, and the reliability of the compressor (17) is improved. In which, a third pressure-detector (48) is provided for detecting a rise in pressure between a compressor (17) and a four-way changeover valve (18), and a control circuit (49) is provided for controlling such that, in the event that the pressure within the pipe is below a predetermined pressure, a sixth valve (45) and a seventh valve (46) are closed, while in the event that the pressure within the pipe exceeds the predetermined pressure, the sixth valve (45) and seventh valve (46) are opened.