Provides is a method of manufacturing an insert-molded article enabling to perform resin molding and tie bar cutting in one step and so as not to expose the cut planes of the tie bars to the external surface of the resin. A lead frame 1 provided with easily breakable notches 3a at positions closer to the metal component than the interfaces of tie bars 3 to be resin molded is prepared and positioned by means of pilot pins 11 provided to a lower mold 10. A metal component 4 is sandwiched between support protrusions 13 and component fixing pins 24 by lowering an upper mold 20 with the lead frame being positioned. Tie bar cutting punches 23 provided to the upper mold 20 are pressed against the tie bars, the tie bars 3 are separated from the metal component 4 by breaking the notches 3a, and the surroundings of the metal component 4 are filled with resin while the molds are closed. By this, the cut surfaces between the metal component 4 and the tie bars 3 are buried in the molded resin 7.