A hydrocarbon compound synthesis reaction unit which synthesizes a hydrocarbon compound by a chemical reaction of a synthesis gas including a hydrogen and a carbon monoxide as the main components, and a slurry having a solid catalyst suspended in liquid hydrocarbons, the hydrocarbon compound synthesis reaction unit is provided with: a reactor which contains the slurry inside, into which the synthesis gas is introduced, and from which the gas after the reaction is discharged from the top thereof; an internal separation device provided inside the reactor to separate the catalyst and the synthesized liquid hydrocarbons in the slurry; and an external separation device provided outside the reactor to separate the catalyst and the liquid hydrocarbons in the slurry which is extracted from the reactor.