A heat pump water heater comprising: a hot water tank in which hot water is stored; hot water tank temperature detecting means for detecting temperature of the hot water in the hot water tank; a heat pump device for heating the hot water; a heating circuit in which the heat pump device is placed at a halfway portion of the heating circuit and which returns the hot water sent from a lower portion of the hot water tank to an upper portion of the hot water tank; a pump provided in the heating circuit between the lower portion of the hot water tank and the heat pump device; operating means for setting a temperature of the hot water heated by the heat pump device between predetermined lower limit temperature and predetermined upper limit temperature; and a control device for executing at least a hot water storing operation mode in which the hot water is heated by the heat pump device to a set temperature which is set by the operating means, and a freezing-preventing operation mode in which the hot water is made to flow to the heating circuit under a predetermined freezing-preventing condition, wherein the control device includes freezing-preventing operation start-determining means for determining a starting condition of the freezing-preventing operation mode, and heating temperature-determining means for determining heating temperature of the hot water in the freezing-preventing operation mode, characterized in that the control device further includes operation state-determining means for determining whether the operating means is in an ON state or an OFF state, and the heating temperature determined by the heating temperature-determining means is changed based on determination of the operation state-determining means. a hot water tank in which hot water is stored; hot water tank temperature detecting means for detecting temperature of the hot water in the hot water tank; a heat pump device for heating the hot water; a heating circuit in which the heat pump device is placed at a halfway portion of the heating circuit and which returns the hot water sent from a lower portion of the hot water tank to an upper portion of the hot water tank; a pump provided in the heating circuit between the lower portion of the hot water tank and the heat pump device; operating means for setting a temperature of the hot water heated by the heat pump device between predetermined lower limit temperature and predetermined upper limit temperature; and a control device for executing at least a hot water storing operation mode in which the hot water is heated by the heat pump device to a set temperature which is set by the operating means, and a freezing-preventing operation mode in which the hot water is made to flow to the heating circuit under a predetermined freezing-preventing condition, wherein the control device includes freezing-preventing operation start-determining means for determining a starting condition of the freezing-preventing operation mode, and heating temperature-determining means for determining heating temperature of the hot water in the freezing-preventing operation mode, characterized in that the control device further includes operation state-determining means for determining whether the operating means is in an ON state or an OFF state, and the heating temperature determined by the heating temperature-determining means is changed based on determination of the operation state-determining means.