PURPOSE: To miniaturize a plant equipment by heating water in an exhaust heat collecting system to a temperature of becoming saturated water by an exhaust heat collecting preheater, and further heating the water by heat of exhaust gas of a fuel reformer to generate steam in a steam generator.

CONSTITUTION: In an exhaust heat collecting preheater 7, water of flowing in an exhaust heat collecting system in a secondary side is heated to saturated water by cell cooling water from a steam separator 5. Here heated water, flowing in a secondary side of a steam generator 3, is further heated by discharge high temperature gas of a fuel reformer 2 to generate steam, and this steam is supplied to the first exhaust heat utilizing device 12. Warm water heated to the saturated water by the preheater 7 is partly supplied to the second exhaust heat utilizing device 14. Condensed water after utilized in these devices 12, 14 is again returned to the preheater 7 by a condensed water circulating pump 15. By the constitution thus provided, a plant equipment is miniaturized further with a low cost and enabled to correspond to manifoldness of utilizing exhaust heat.