A home fuel gas refining system has a modifier for modifying a hydrogen-containing fuel to produce a modified gas. The modifier includes a hydrogen-containing fuel supply mechanism for supplying the hydrogen-containing fuel and a modifying air supply mechanism for supplying modifying air. The hydrogen-containing fuel delivered from the hydrogen-containing fuel supply mechanism and the modifying air delivered from the modifying air supply mechanism are mixed with each other by a modification fuel ejector, and then delivered to a reactor.