A production method of liquid hydrocarbons from natural gas, comprising: a hydrodesulfurization step of removing sulfur compounds in natural gas by hydrodesulfurization; a synthesis gas production step of producing synthesis gas by way of a reforming reaction of the natural gas after the hydrodesulfurization with steam and/or carbon dioxide; a Fischer-Tropsch oil production step of producing Fischer-Tropsch oil from the synthesis gas by subjecting the synthesis gas produced from the synthesis gas production step to a Fischer-Tropsch reaction; an upgrading reaction step of hydrogenating the Fischer-Tropsch oil produced from the Fischer-Tropsch oil production step; an upgrading gas/liquid separation step of subjecting the hydrogenated product obtained by the upgrading reaction step to gas/liquid separation to obtain liquid hydrocarbons; a shift step of partly branching the synthesis gas produced from the synthesis gas production step to form a branch line at a stage prior to getting to the Fischer-Tropsch oil production step and raising the hydrogen concentration by subjecting the synthesis gas into the branch line to a water gas shift reaction; and a hydrogen separation step of separating the high-purity hydrogen from the outlet gas of the shift step and also isolating the consequently produced residual gas, wherein the residual gas separated in the hydrogen separation step is circulated to the synthesis gas production step in order to use it as raw material for synthesis gas production, the residual gas containing methane and carbon dioxide as main components; wherein the high-purity hydrogen gas separated in the hydrogen separation step is supplied to the hydrodesulfurization step and the upgrading reaction step. a hydrodesulfurization step of removing sulfur compounds in natural gas by hydrodesulfurization; a synthesis gas production step of producing synthesis gas by way of a reforming reaction of the natural gas after the hydrodesulfurization with steam and/or carbon dioxide; a Fischer-Tropsch oil production step of producing Fischer-Tropsch oil from the synthesis gas by subjecting the synthesis gas produced from the synthesis gas production step to a Fischer-Tropsch reaction; an upgrading reaction step of hydrogenating the Fischer-Tropsch oil produced from the Fischer-Tropsch oil production step; an upgrading gas/liquid separation step of subjecting the hydrogenated product obtained by the upgrading reaction step to gas/liquid separation to obtain liquid hydrocarbons; a shift step of partly branching the synthesis gas produced from the synthesis gas production step to form a branch line at a stage prior to getting to the Fischer-Tropsch oil production step and raising the hydrogen concentration by subjecting the synthesis gas into the branch line to a water gas shift reaction; and a hydrogen separation step of separating the high-purity hydrogen from the outlet gas of the shift step and also isolating the consequently produced residual gas, wherein the residual gas separated in the hydrogen separation step is circulated to the synthesis gas production step in order to use it as raw material for synthesis gas production, the residual gas containing methane and carbon dioxide as main components; wherein the high-purity hydrogen gas separated in the hydrogen separation step is supplied to the hydrodesulfurization step and the upgrading reaction step.