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 , 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 , the plurality of refrigerant flow-in/out holes are all closed, which corresponds to a valve-closed state. <EOS>