An improvement in a method of pyrolysis wherein an organic material, such as city waste, is pyrolyzed using a two-bed type pyrolysis system including a fluidized bed type pyrolysis reactor and a combustion reactor and wherein energy is recovered from burning the pyrolysis gases produced is disclosed. The improvement comprises recovering the heat of a combustion exhaust gas which is generated when the energy of the pyrolysis gas is recovered, heating a fluid medium with the recovered heat, and heating the organic material to be pyrolyzed with the heated fluid heat medium to dry the organic material before it is pyrolyzed.