A refrigeration cycle apparatus comprising: a first refrigeration cycle unit and a second refrigeration cycle unit disposed in a common circulation path for a heat medium, each of the first refrigeration cycle unit and the second refrigeration cycle unit having an independent refrigerant circuit using refrigerant, each of the first refrigeration cycle unit and the second refrigeration cycle unit being configured to control temperature of the heat medium; and a control device configured to control a heating capacity during a heating operation and a defrosting capacity during a defrosting operation of each of the first refrigeration cycle unit and the second refrigeration cycle unit, wherein when a first defrosting start condition is satisfied, the control device is configured to determine the defrosting capacity in the defrosting operation of the first refrigeration cycle unit, and start the defrosting operation, the defrosting capacity of the first refrigeration cycle unit is determined to fall within a range satisfying a first determination condition and within a range satisfying a second determination condition, the first determination condition is a condition that a sum of a load capacity of a load device using heat of the heat medium when the first defrosting start condition is satisfied, and the defrosting capacity of the first refrigeration cycle unit does not exceed the heating capacity of the second refrigeration cycle unit, and the second determination condition is a condition that a sum of an inter-unit defrosting interval, and a defrosting period of the first refrigeration cycle unit does not exceed a shortest defrosting interval of the second refrigeration cycle unit, the shortest defrosting interval being a period when the second refrigeration cycle unit is operated at an upper limit of the heating capacity, the inter-unit defrosting interval being a period from a time when the defrosting operation of the second refrigeration cycle unit is completed to a time when the first defrosting start condition is satisfied. a first refrigeration cycle unit and a second refrigeration cycle unit disposed in a common circulation path for a heat medium, each of the first refrigeration cycle unit and the second refrigeration cycle unit having an independent refrigerant circuit using refrigerant, each of the first refrigeration cycle unit and the second refrigeration cycle unit being configured to control temperature of the heat medium; and a control device configured to control a heating capacity during a heating operation and a defrosting capacity during a defrosting operation of each of the first refrigeration cycle unit and the second refrigeration cycle unit, wherein when a first defrosting start condition is satisfied, the control device is configured to determine the defrosting capacity in the defrosting operation of the first refrigeration cycle unit, and start the defrosting operation, the defrosting capacity of the first refrigeration cycle unit is determined to fall within a range satisfying a first determination condition and within a range satisfying a second determination condition, the first determination condition is a condition that a sum of a load capacity of a load device using heat of the heat medium when the first defrosting start condition is satisfied, and the defrosting capacity of the first refrigeration cycle unit does not exceed the heating capacity of the second refrigeration cycle unit, and a load capacity of a load device using heat of the heat medium when the first defrosting start condition is satisfied, and the defrosting capacity of the first refrigeration cycle unit does not exceed the heating capacity of the second refrigeration cycle unit, and the second determination condition is a condition that a sum of an inter-unit defrosting interval, and a defrosting period of the first refrigeration cycle unit does not exceed a shortest defrosting interval of the second refrigeration cycle unit, the shortest defrosting interval being a period when the second refrigeration cycle unit is operated at an upper limit of the heating capacity, the inter-unit defrosting interval being a period from a time when the defrosting operation of the second refrigeration cycle unit is completed to a time when the first defrosting start condition is satisfied. an inter-unit defrosting interval, and a defrosting period of the first refrigeration cycle unit does not exceed a shortest defrosting interval of the second refrigeration cycle unit, the shortest defrosting interval being a period when the second refrigeration cycle unit is operated at an upper limit of the heating capacity, the inter-unit defrosting interval being a period from a time when the defrosting operation of the second refrigeration cycle unit is completed to a time when the first defrosting start condition is satisfied.