The present disclosure relates to a facility for forming a wood plastic composite by mixing and extruding wood powder and a polymer resin. According to a facility of the present disclosure, in a process of forming a wood plastic composite, gas and water vapor contained in wood powder and polymer resin are efficiently removed, and thus, a coupling force between wood powder and polymer resin increases, and also, wood powder is uniformly dispersed inside polymer resin, and thus, physical properties of a wood plastic composite to be formed is not degraded, and in addition, since there is no stagnant section while molten liquid of wood powder and polymer resin passes through each apparatus in the facility, wood powder is prevented from carbonizing or polymer resin is prevented from solidifying, and thus, physical properties of the wood plastic composite to be formed are maintained constant.