Disclosed are a porous electroformed shell for forming a grain pattern and a manufacturing method thereof. The method includes the step of implanting a fiber into a patterned surface of a negative-type silicone cast; applying, laminating, and curing an epoxy resin on the patterned surface of the negative-type silicone cast, and transferring the fiber from the negative-type silicone cast to an epoxy mandrel during demolding of the epoxy mandrel; forming a conductive thin film on the patterned surface of the epoxy mandrel, and causing the patterned surface to be conductive; removing the fiber having the conductive thin film from a surface of the epoxy mandrel; forming an electrodeposited layer by electrodepositing an electroforming metal on the conductive thin film while generating and growing a fine pore at a position of a hole due to the removal of the fiber; and demolding the electrodeposited layer having the fine pore from the epoxy mandrel. Through the disclosed method, precise control on a diameter and distribution of a fine pore can be simply and efficiently can be carried out.