In a fluid transmission device in which a core is fixed to inner ends of a plurality of blades so as to form, together with a bowl-shaped shell and the blades, an impeller, the core including a plurality of latching holes with which a projecting piece projectingly provided at the inner end of the blade is latched and including a balance weight chip welded to the core, the balance weight chip includes a projecting piece-avoiding hole through which a portion, projecting from the latching hole, of the projecting piece extends, the balance weight chip being welded to the core with a whole of the balance weight chip in intimate contact with the core.