A method for manufacturing a fluid power transmission includes a first step of assembling a blade/core provisional assembly having a plurality of blades movably linked to a core, involving aligning the plurality of blades on a blade alignment jig, laying the core over a group of blades while extending a projecting piece provided on each blade through a latching hole provided in the core, and bending an extremity part of the projecting piece thus preventing the projecting piece from coming out of the latching hole, a second step of setting the blade/core provisional assembly at a predetermined position on an inside face of the shell, and a third step of carrying out brazing between the projecting piece and the latching hole and between the blade and the shell. Such method provides a high quality impeller of a fluid power transmission by joining a shell, a blade, and a core.