The invention discloses a dual-heating non-catalytic methane synthesizing gasifier, and belongs to the field of natural gas producing equipment. An outside-kiln heating device conducts heat to a material in a hearth through a rotary kiln shell to generate an external heating effect. After fuel is dried and crushed, the fuel is sent into a dry distillation zone of the gasifier and is pyrolyzed in the dry distillation zone to obtain a large amount of combustible gas mainly containing CmHn, and the CmHn gas flows to an oxidation zone; a proper amount of oxygen is sent into the oxidation zone, thecombustible gas and the oxygen are mixed and combusted to generate an internal heating effect, the external heating effect enables the oxidation zone to obtain the precise temperature of 1020+/-10 DEG C, the CmHn is fully cracked into CH2 and H2 and flows to a reduction zone; constant temperature is obtained in the reduction zone, and a large amount of CH4 is synthesized from the CH2 and the H2 in a reducing atmosphere without the need of a catalyst as well as expensive investment and running cost of a methanation facility, so that the coal-to-natural gas project investment is 70% lower thanthat in the existing technology, the running cost is reduced by 50%, and thus biomass such as domestic garbage, straw and organic sludge can be directly converted into natural gas.