A fast earthing switch device for HV applications which includes a gas-tight casing, a movable contact connectable to and unconnectable from a fixed contact. The movable contact is linearly movable between an open position and a closed position. The device further includes an operating mechanism for the movable contact and is characterized in that the operating mechanism includes an actuating spring actuating a closing operation of the movable contact from the open position to the closed position, at least a driving lever mounted on an operating shaft actuating an opening operation of the movable contact from the closed position to the open position, the driving lever also partially reloading the actuating spring during the opening operation, the operating mechanism further includes coupling means operatively coupling the driving lever to the movable contact.