Abstract: A heat pump type air conditioner having a heat gas engine having a radiator and a cooler, an outdoor heat exchanger provided in an outdoor unit and an indoor heat exchanger provided in an indoor unit, is further provided with a heat exchanger in the outdoor unit and/or the indoor unit, and control means for controlling water flow in first and second passages so as to perform cooling/heating operation. When slightly-heating or slightly-cooling dry operation or defrosting operation is required, a part of the hot water from the radiator is allowed to selectively flow through the second fluid passage into the heat exchanger by adjusting opening degree of open/close valves disposed between the first and second fluid passages.