A gas-insulated switchgear device comprising a first casing housing: at least a first terminal for input/output connection; a disconnector unit comprising at least a first fixed contact operatively coupled to said first terminal and a corresponding first movable contact which can be electrically connected/disconnected with said first fixed contact, during operation of the disconnector unit; a circuit breaker unit electrically connected to said disconnector unit and comprising at least a couple of interruption contacts (10, 11) which can be actuated, during operation of said circuit breaker unit, between a circuit breaker closed position where they are electrically coupled and a circuit breaker open position where they are electrically separated; actuating means for operating said disconnector unit and said circuit breaker unit; a second casing operatively coupled with said actuating means, which houses said interruption contacts (10, 11) and on the outer surface of which at least said first movable contact is mounted; characterized in that said second casing is pivotally mounted inside said first casing so as to rotate said first movable contact during operation of said disconnector unit, said couple of interruption contacts (10, 11) being operatively coupled to said actuating means so as to be kept electrically coupled in said circuit breaker closed position and substantially still relative to each other during rotation of said second casing, and further characterized in that said couple of interruption contacts (10, 11) comprises a first main contact and a second main contact; said actuation means comprise:. shaft means operatively coupled with rotation driving means and solidly connected to said first main contact and to the second casing at a first end of the second casing,. rod-shaped means comprising a first rod portion connected to said second main contact and a second rod portion operatively connected to translation driving means at the other end of the second casing, said first and second rod portions (16, 17) being substantially aligned along said longitudinal axis; whereby the coupling means comprise two thrust bearings and are configured so as to mechanically connect the second casing respectively on one side with the main contact and the shaft means, and on the other side with the rod-shaped means (16,17) by realizing a turning kinematic pair during rotation of the second casing, and by realizing a sliding kinematic pair during operation of the circuit breaker unit; so that in use: - during rotation of the second casing, the couple of interruption contacts (10,11) are kept still and motionless, and electrically coupled in the circuit breaker closed position, - and during the translation of the couple of interruption contacts (10,11) relatively to each other along the axis during opening/closing operations of said circuit breaker unit, the second casing is kept substantially still.. shaft means operatively coupled with rotation driving means and solidly connected to said first main contact and to the second casing at a first end of the second casing,. rod-shaped means comprising a first rod portion connected to said second main contact and a second rod portion operatively connected to translation driving means at the other end of the second casing, said first and second rod portions (16, 17) being substantially aligned along said longitudinal axis; - during rotation of the second casing, the couple of interruption contacts (10,11) are kept still and motionless, and electrically coupled in the circuit breaker closed position, - and during the translation of the couple of interruption contacts (10,11) relatively to each other along the axis during opening/closing operations of said circuit breaker unit, the second casing is kept substantially still.