Abstract: There is provided an efficient steam generation system capable of reducing a temperature difference in heat to be drawn by a heat pump. A first heat pump (2) includes a first evaporator (7) and a second evaporator (8). A second heat pump (3) is connected to the first heat pump (2) via an uppermost condenser (10) serving as the first evaporator (7). A heat source fluid is passed through a second evaporator (8) of the first heat pump (2) and an evaporator (12) of the second heat pump (3) in sequence. Then, steam is generated by application of heat to water in a condenser (5) of the first heat pump (2).