PURPOSE: To perform a feeding of hot water of higher temperature and get a high efficiency during adding of hot water into a bath tub by a method wherein this operation is carried out with means to cause orders of flowing of water supplied to each of a plurality of heat exchangers constituting a plurality of circulation circuits to be the same for every refrigerant cycle in a plurality of circulating circuits.

CONSTITUTION: A plurality of refrigerant cycles 30 and 40 are constructed such that each of compressors 31, 41, the first heat exchangers 32, 42, the second heat exchangers 33, 43, metering devices 34, 44 and the third heat exchangers 35, 45 are communicated to each other in sequence by refrigerant pipes 36, 46. In addition, the first and second hot water storing tanks 50 and 51 to which the water storing part is communicated are mounted. In addition, each of a plurality of the first and second heat exchangers 32, 42 ; and 33, 43 connected in series with each other is provided with the first and second circulation circuits 60, 70 for circulating water in the first and second hot water storing tanks 50, 51. Order of flowing water supplied to each of the first and second heat exchangers 32, 42; 33, 43 constituting the first and second circulation circuits 60, 70 is made same for every refrigerant cycles 30, 40 through each of the first and second circulation circuits 60, 70.