NOVELTY - A fuel gas manufacturing apparatus has a modifier for modifying a hydrogen-containing fuel to produce a modified gas; a refiner with a pressure swing adsorption (PSA) mechanism for removing unwanted materials from the modified gas to refine a hydrogen-rich fuel gas; and a residual gas supply mechanism for supplying a residual gas from a tower of the PSA mechanism to a heater. The supply mechanism has a residual gas passage, and a branch passage.    USE - For manufacturing a fuel gas.    ADVANTAGE - The apparatus requires no off-gas tank and is of a simple arrangement capable of reliably controlling the flow rate of an off gas supplied to the heater.    DETAILED DESCRIPTION - A fuel gas manufacturing apparatus (10) comprises:    (a) a modifier for modifying a hydrogen-containing fuel to produce a modified gas;    (b) a refiner including a PSA mechanism for removing unwanted materials from the modified gas to refine a hydrogen-rich fuel gas; and    (c) a residual gas supply mechanism (90) for supplying a residual gas from a tower of the PSA mechanism to a heater.    The residual gas supply mechanism comprises a residual gas passage (92) connected to the PSA mechanism and the heater, and a branch passage (94) having opposite ends connected to the residual gas passage and branched from the residual gas passage. The branch passage has a chamber for storing the residual gas.    An INDEPENDENT CLAIM is also included for a method of operating the fuel gas manufacturing apparatus comprising the modifier, the refiner and the residual gas supply mechanism that includes the residual gas passage, a flow rate adjusting mechanism (96) and the branch passage having the chamber and a valve (38b, 80, 86), comprising when the residual gas is discharged from the PSA mechanism, closing the valve to store part of the residual gas in the chamber and opening the flow rate adjusting mechanism to supply the remainder of the residual gas to the heater; and when the residual gas is not discharged from the PSA mechanism, opening the valve to supply the residual gas stored in the chamber to the heater.    DESCRIPTION OF DRAWING(S) - The figure is a block diagram of a home fuel gas refining system as a fuel gas manufacturing apparatus.    Fuel gas manufacturing apparatus (10)    Valve (38b, 80, 86)    Residual gas supply mechanism (90)    Residual gas passage (92)    Branch passage (94)    Flow rate adjusting mechanism (96)    On-off valve (102)