A method and a device for producing synthetic natural gas are provided. According to processes of the method, a raw material gas is preheated and separated into two parts, the first part of the raw material gas is fed into the upper part of a first methanation reactor after being mixed with a first heated recycle gas, the second part of the raw material gas is fed to the middle part of the first methanation reactor after being mixed with a second recycle gas so as to obtain a first product gas, the first product gas is cooled and separated into two parts, namely a first first-product gas and a second first-product gas, the first first-product gas is pressurized by a recycle compressor and then is separated into a first recycle gas and a second recycle gas, the second first-product gas is heated and fed into a second methanation reactor, and a second product gas is cooled and subjected to gas liquid separation to obtain a product gas. The method is reasonable in process and high in operationality and is advantaged by a high comprehensive energy utilization rate, capability of saving energy, environment protection, and the like.