The invention relates to a solid fuel decoupled fluidized bed gasifying method and a gasifying apparatus. By physically separately performing drying and pyrolyzing of fuel, gasification of char, and tar/hydrocarbon reforming, the interactions between the separated chemical reactions and physical processes during fluidized bed gasification can be utilized. Specifically, in a fluidized bed reactor having two reaction chambers, drying and pyrolyzing of fuel, gasification of char, and tar/hydrocarbon reforming are performed, respectively, the reforming of tar/hydrocarbon is promoted through the catalytic effect of the char, and the evaporated fuel moisture is provided to the char gasification and tar/hydrocarbon reforming as an effective reaction agent. Accordingly, the tar content in product gas can be reduced, the use amount of external steam can be reduced, the overall efficiency of gasification can be improved, and this technique can also be applied to the processing of high water-containing fuel. This gasifying method not only can be applied to individual fluidized bed gasification, but can contribute to the design of a combustor that combusts unreacted char, and to advanced decoupled fluidized bed gasification.