PURPOSE: To prevent invasion of moisture and impurity such as Na and Cl ions, etc., into a device by injecting drop-shaped resin into the interface gap occurring at the interface between the sealing resin outside and the exposed member so as to fill the interface gap.

CONSTITUTION: A semiconductor device 10 wherein leads are molded is put in a beaker 12 wherein liquid-form silicon resin 9 is put, and the beaker 12 is placed in a pressurizing vessel 13. After sealing the vessel 13, this is depressurized by a valve 13a, and is pressurized and returned to normal pressure by a valve 13b. The device 10 is taken out of the resin 9, and is cleaned and dried in the air, with which the gap sealing process is finished. The resin 9 is injected and formed in the gap 8 at the interface 7 between resin 6 and a lead 5. Accordingly, the inversion of moisture, impurity ions, etc., in mounting, etc., is prevented by the resin 9.