The invention provides a heat pump water heater. A water storage tank of the heat pump water heater comprises a first liner and a second liner which are communicated with each other, a water outlet is formed in the first liner, and a water inlet is formed in the second liner; a first heat exchanger is arranged on the first liner, a second heat exchanger is arranged on the second liner, a valve body is arranged among a first end port of the first heat exchanger, a first end port of the second heat exchanger and an exhaust port of the compressor, and the valve body can control the first end port of the first heat exchanger or the first end port of the second heat exchanger to be communicated with the exhaust port of the compressor. According to the heat pump water heater, the water storage tank is arranged to be of a double-liner structure, in the defrosting process, coolants merely conduct heat exchange with water inside the second liner through the second heat exchanger, the defrosting efficiency is raised, the defrosting time is shortened, heat loss of the first liner is avoided, replenished cold water is prevented from conducting direct heat convection with hot water in the first liner, thereby in the whole defrosting process, the temperature of water in the first liner is maintained constant, and the comfortableness of a user for using the water is improved.