A resin component for encapsulating a semiconductor includes magnetic powder and silica powder whose average particle diameter is smaller than the average particle diameter of the magnetic powder. Thus, the curing body of the resin component for encapsulating a semiconductor has an electromagnetic wave shielding function by the magnetic powder. Since the spaces of the magnetic powder are filled with the silica powder whose average particle diameter is small, the moldability of the curing body is improved and the insulating characteristics thereof are enhanced. Such a resin component for encapsulating a semiconductor is employed, there can be produced a preferably formed and encapsulated semiconductor device having the electromagnetic wave shielding function and having no malfunction generated due to leakage current from a semiconductor element.