A valve device comprising: a case having an opened bottom portion and a receiving space formed therein; a rotor arranged in the receiving space and including a rotor shaft; a pinion gear coupled to the rotor shaft and to be rotated along with the rotor; a pad gear arranged on a side of the pinion gear to be engaged with the pinion gear, and to be rotated by the pinion gear, the pad gear including a pad valve shaft, which is a rotation shaft of the pad gear; a base plate to cover the open bottom portion of the case; a flow-in pipe coupled to the base plate for introducing a refrigerant to the receiving space therethrough; a boss installed to the base plate and including a plurality of refrigerant flow-in/out holes through which the introduced refrigerant flows in/out; a plurality of flow-in/out pipes coupled to the plurality of refrigerant flow-in/out holes and through which the introduced refrigerant flows in/out; and a pad arranged on the boss to be coupled to the pad valve shaft, the pad including an open cavity formed therein to selectively open one of the plurality of refrigerant flow-in/out holes and a connection cavity formed therein to selectively connect two of the plurality of refrigerant flow-in/out holes, wherein the plurality of refrigerant flow-in/out holes comprises a first refrigerant flow-in/out hole, and a second refrigerant flow-in/out hole, a third refrigerant flow-in/out hole and a fourth refrigerant flow-in/out hole formed in positions sequentially rotated 90 degrees counterclockwise starting from the first refrigerant flow-in/out hole based on the center of the boss, characterized in that when the open cavity is located in between the first and fourth refrigerant flow-in/out holes (83, 86), the plurality of refrigerant flow-in/out holes are all closed, which corresponds to a valve-closed state. a case having an opened bottom portion and a receiving space formed therein; a rotor arranged in the receiving space and including a rotor shaft; a pinion gear coupled to the rotor shaft and to be rotated along with the rotor; a pad gear arranged on a side of the pinion gear to be engaged with the pinion gear, and to be rotated by the pinion gear, the pad gear including a pad valve shaft, which is a rotation shaft of the pad gear; a base plate to cover the open bottom portion of the case; a flow-in pipe coupled to the base plate for introducing a refrigerant to the receiving space therethrough; a boss installed to the base plate and including a plurality of refrigerant flow-in/out holes through which the introduced refrigerant flows in/out; a plurality of flow-in/out pipes coupled to the plurality of refrigerant flow-in/out holes and through which the introduced refrigerant flows in/out; and a pad arranged on the boss to be coupled to the pad valve shaft, the pad including an open cavity formed therein to selectively open one of the plurality of refrigerant flow-in/out holes and a connection cavity formed therein to selectively connect two of the plurality of refrigerant flow-in/out holes, wherein the plurality of refrigerant flow-in/out holes comprises a first refrigerant flow-in/out hole, and a second refrigerant flow-in/out hole, a third refrigerant flow-in/out hole and a fourth refrigerant flow-in/out hole formed in positions sequentially rotated 90 degrees counterclockwise starting from the first refrigerant flow-in/out hole based on the center of the boss, characterized in that when the open cavity is located in between the first and fourth refrigerant flow-in/out holes (83, 86), the plurality of refrigerant flow-in/out holes are all closed, which corresponds to a valve-closed state.