A CHP system includes a combustor (heat source), a Rankine cycle apparatus, and a second heat exchanger. The Rankine cycle apparatus includes, as an evaporator, a first heat exchanger that absorbs thermal energy produced in the combustor. The second heat exchanger is located closer to the combustor than is the evaporator, absorbs thermal energy produced in the combustor, and transfers the thermal energy to a heat medium.

At a center portion of a ceiling wall of a furnace body having a lateral wall between the ceiling wall and a bottom wall, there is a burner that combusts downwards. A reforming reaction tube is provided in a circumference of the burner to carry out a steam reforming treatment on a source gas. A discharging portion is an opening at an upper side portion of the lateral wall for discharging combustion gas of the burner. A cylindrical outer wall is disposed at an outer side portion of the lateral wall. In an outside space formed between the lateral wall and the outer wall, there is a steam generating heat exchanger generating steam or a mixture gas of a source gas and steam. At a lower side portion of the outer wall, there is outside discharging opening discharging the combustion gas which flows through the outside space.

At a center portion of a ceiling wall of a furnace body having a lateral wall between the ceiling wall and a bottom wall, there is a burner that combusts downwards. A reforming reaction tube is provided in a circumference of the burner to carry out a steam reforming treatment on a source gas. A discharging portion is an opening at an upper side portion of the lateral wall for discharging combustion gas of the burner. A cylindrical outer wall is disposed at an outer side portion of the lateral wall. In an outside space formed between the lateral wall and the outer wall, there is a steam generating heat exchanger generating steam or a mixture gas of a source gas and steam. At a lower side portion of the outer wall, there is outside discharging opening discharging the combustion gas which flows through the outside space.