A lost-wax cast impeller for a supercharger having no parting line on a hub surface and a blade surface in each space demarcated by pairs of long blades adjacent to each other and having excellent aerodynamic performance. A method of manufacturing the impeller involves forming a lost form pattern in substantially the same shape as the impeller, forming a mold by eliminating the lost form pattern after the lost form pattern is coated with a refractory, and pouring a molten metal in the mold for casting. In the molding step, lost material is injection-molded in a space demarcated by radially arranging, toward a center shaft, a plurality of slide molds having short blade-shaped bottomed groove parts and space shapes between the pairs of long blades adjacent to each other, and the slide molds are released by moving in the radial direction of the center shaft while rotating.