The objective of the present invention is to provide a composite impeller with uniform reproducibility and quality by integrally molding a 3D composite material and performing precision machining. To this end, the present invention is characterized by comprising: a planar composite acquisition step of obtaining a fabric-like composite through weaving using a warp yarn and a weft yarn that are made of carbon fiber or glass fiber; a multi-layer composite acquisition step of laminating the planar composite in a plurality of layers; a bulk composite acquisition step of stitching the multi-layer composite in the vertical direction with a needle yarn, in which stitching positions are arranged to intersect up and down so as to obtain a bulk composite having a constant thickness; a block composite molded product acquisition step of putting the bulk composite into a mold, sealing the mold with a vacuum bag for resin injection, injecting a resin in a vacuum state by controlling the viscosity of the resin, and then curing the resin at a certain temperature to form a composite having a standard shape; and an impeller processing step of processing the block composite molded product into an impeller shape by means of a five-axis processing machine.