NOVELTY - A battery stack (5) has air pole (5b) to which fuel electrode (5a), air gas having oxygen component, heating gas containing hydrocarbon and hydrogen component are supplied. Hydrocarbon component of ejected heating gas is modified by modifier (2) by water vapor and CO component is removed by CO transformer (3). Battery stack (4) generating electricity by transformer using heating gas, removes CO component.    USE - Fuel cell power generating device for generating electricity.    ADVANTAGE - By modifying the hydrocarbon component of ejected heating gas by modifier using water vapor and removing CO component using CO transformer, the recovery of hydrogen increases and by supplying CO component heating gas to another battery stack is removable, thus electricity generation efficiency increases. The thermal efficiency is increased by preheating the ejected heating gas before supplying to other battery stack.    DETAILED DESCRIPTION - A pair of battery stacks (4,5) contains air poles (4b,5b) and fuel electrodes (5a,4a) to which air gas and heating gas are respectively supplied. The heating gas is preheated using a preheater before supplying to the battery stack air poles (5b,4b) respectively. The battery stack (5) generates electricity using heating gas and then the gas is ejected. The hydrocarbon component of ejected gas is modified by using a modifier (2). A deoxidation device is arranged on upstream side of battery stack (5) to remove CO component from ejected heating gas. A condenser is arranged on downstream side of the battery stack (5) which condenses the unnecessary acid component present in the heating gas and it is removed. An ejector is arranged on downstream side of battery stack (5) to rise the heating gas pressure ejected from fuel electrode (5a). The heating gas is again preheated and supplied to another CO transformer arranged on upstream side of battery stack (5) to remove CO component present in the heating gas. The ejected heating gas without CO component is preheated and supplied to another battery stack air pole (4b) to generate further electricity. A primary pressure reducing regulating valve is arranged between battery stack (5) and an ejector which is controlled so that differential pressure between fuel electrode poles of battery stack (5) and air pole (5b) is at preset range.    DESCRIPTION OF DRAWING(S) - The figure shows the system flow chart showing fuel cell power generating device. (Drawing includes non-English language text).    Modifier (2)    CO transformer (3)    Battery stacks (4,5)    Fuel electrodes (4a,5a)    Air poles (4b,5b)