An electronic authentication system includes a vehicle-side control unit that judges whether ID information of an electronic key is identical to vehicle-side ID information, an ignition switch unit that permits engine starting operation and handle unlocking operation on the basis of the identity of the ID information of the electronic key to the vehicle-side ID information, and an actuator that unlocks an opening and closing lid such as a accommodation box lid. These component members are attached and fixed to a leg shield (an inner leg shield) and modularized. These members are preassembled into the inner leg shield and modularized like this, whereby the assembling work into the vehicle becomes very easy and it is possible to make the assembling work efficient to a great extent.