To provide an engine driven heat pump air conditioner which can be downsized and is inexpensive while enhancing refrigerating efficiency.

A compression refrigerating cycle is constituted by connecting a compressor 2 driven by an engine 1, a first outdoor heat exchanger 3, an evaporator 4, an expansion valve 5, and an indoor unit 6 in series. A liquid reservoir 12 is connected to a vapor generator 9 vaporizing operation medium liquid by the heat of the engine cooling water via the first liquid piping 11 into which a liquid supply pump 10 is interposed and the second outdoor side heat exchanger 14 and the evaporator 4 are connected to the liquid reservoir 12. The vapor generator 9 and the second outdoor side heat exchanger are connected via the first vapor piping 19 into which an ejector 18 is interposed, the evaporator 4 is connected to the ejector 18 via the second vapor piping 20, operation medium vapor is sucked and fed to the second outdoor side heat exchanger 14 from in the evaporator 4 by back pressure when jetting and feeding vapor to the second outdoor side heat exchanger 14 side from the vapor generator 9 by the ejector 18.