A shielded electronic component including a wiring board, at least one semiconductor chip mounted on a main surface of the wiring board, a sealant which seals the whole of an upper surface of the wiring board, and a nickel (Ni) plating film formed on an upper surface of the sealant is provided. The Ni plating film is formed on a palladium (Pd) pretreatment layer formed on the upper surface of the sealant with using high-pressure CO2 in a state of protecting a back surface of the wiring board, and is electrically connected with an end portion of a ground wiring layer of the wiring board or a ground (GND) connection through-hole connected with the end portion of the ground wiring layer.