A lock system includes a lock mechanism for holding a lid element in a locked state, an electric actuator for driving the lock mechanism to an unlocking side based on an operation of an open switch, and a key cylinder adapted to be operated to rotate by a key so as to be switched through the rotational operation to an “UNLOCK” position where the open switch is enabled to function and a “LOCK” position where the open switch is disabled from functioning, whereby unlocking of the lid element is prohibited through a rotational operation of the key cylinder to the “LOCK” position. An operating unit of the lock system causes the key cylinder and the lock mechanism to be mechanically linked with each other by a wire cable, whereby the lock mechanism is forcibly driven to the unlocking side through a rotational operation of the key cylinder to the “OPEN” position.