A heat storing apparatus having a cascade cycle, comprising: a heat pump having a low-temperature cooling cycle in which a first refrigerant is circulated to a first inverter compressor , a cascade heat exchanger , a first expansion mechanism , and an outdoor heat exchanger and the first refrigerant evaporates a second refrigerant while passing through the cascade heat exchanger and a high-temperature cooling cycle in which the second refrigerant is circulated to a second inverter compressor , a heat storage heat exchanger , a second expansion mechanism , and the cascade heat exchanger and the second refrigerant heats a heat medium while passing through the heat storage heat exchanger ; a heat storage tank connected with the heat storage heat exchanger through a heat medium path; an outdoor temperature sensor sensing an outdoor temperature; and a controller adapted to set a target heat storage temperature of the heat storage tank , characterized in that the controller is adapted to set the target heat storage temperature between a minimum target heat storage temperature and a maximum target heat storage temperature, and to set the maximum target heat storage temperature as the target heat storage temperature when the outdoor temperature is equal to or lower than a lowerlimit set temperature and the minimum target heat storage temperature as the target heat storage temperature when the outdoor temperature is equal to or higher than an upperlimit set temperature, wherein the controller is adapted to set the target heat storage temperature to be inversely proportionate to the outdoor temperature when the outdoor temeprature is higher than the lowerlimit set temperature and lower than the upperlimit set temperature. a heat pump having a low-temperature cooling cycle in which a first refrigerant is circulated to a first inverter compressor , a cascade heat exchanger , a first expansion mechanism , and an outdoor heat exchanger and the first refrigerant evaporates a second refrigerant while passing through the cascade heat exchanger and a high-temperature cooling cycle in which the second refrigerant is circulated to a second inverter compressor , a heat storage heat exchanger , a second expansion mechanism , and the cascade heat exchanger and the second refrigerant heats a heat medium while passing through the heat storage heat exchanger ; a heat storage tank connected with the heat storage heat exchanger through a heat medium path; an outdoor temperature sensor sensing an outdoor temperature; and a controller adapted to set a target heat storage temperature of the heat storage tank , characterized in that the controller is adapted to set the target heat storage temperature between a minimum target heat storage temperature and a maximum target heat storage temperature, and to set the maximum target heat storage temperature as the target heat storage temperature when the outdoor temperature is equal to or lower than a lowerlimit set temperature and the minimum target heat storage temperature as the target heat storage temperature when the outdoor temperature is equal to or higher than an upperlimit set temperature, wherein the controller is adapted to set the target heat storage temperature to be inversely proportionate to the outdoor temperature when the outdoor temeprature is higher than the lowerlimit set temperature and lower than the upperlimit set temperature. <EOS>