To provide a method of pseudogrounding which is capable of protecting against EMI by pseudogrounding communication lines, etc. without necessity of expensive ferrite cores and increasing the number of steps and cost. A wiring which is connected to an LSI (43) on a package and is connected to an external wiring (47) via a connector (461), radio-frequency connected via a capacitance (451, 452) to ta housing (42) in which protection against EMI is achieved so that the radiated noise energy is not higher than EMI restricted value level. This enables said wiring to be pseudogrounded.