A refrigerator comprising: a cabinet that defines a first storage compartment; a first door that is opened or closed to allow or prevent access to an interior of the first storage compartment, the first door being rotatably coupled to the cabinet through a hinge assembly, a storing device coupled to the first door to define a second storage compartment, wherein, when the first door is closed, the second storage compartment is disposed in the first storage compartment; and a second door rotatably connected to the first door and configured to be opened or closed to allow or prevent access to an interior of the second storage compartment, wherein the interior of the second storage compartment is accessible when the first door is closed and the second door is opened, wherein the first door includes a plurality of first coupling parts (330, 331, 332) to which the storing device is coupled, characterized in that a left and right width of the second door is identical to the left and right width of the first door, wherein a rotation direction of the second door is identical to a rotation direction of the first door, wherein the storing device includes: a frame; and a basket (510, 540, 560) installed on the frame, wherein each of the frame and the basket (510, 540, 560) includes at least one second coupling part (425, 445) interacting with at least one of the plurality of first coupling parts (330, 331, 332), wherein a front surface of the second door is positioned to be generally coplanar with at least a portion of a front surface of the first door. a cabinet that defines a first storage compartment; a first door that is opened or closed to allow or prevent access to an interior of the first storage compartment, the first door being rotatably coupled to the cabinet through a hinge assembly, a storing device coupled to the first door to define a second storage compartment, wherein, when the first door is closed, the second storage compartment is disposed in the first storage compartment; and a second door rotatably connected to the first door and configured to be opened or closed to allow or prevent access to an interior of the second storage compartment, wherein the interior of the second storage compartment is accessible when the first door is closed and the second door is opened, wherein the first door includes a plurality of first coupling parts (330, 331, 332) to which the storing device is coupled, characterized in that a left and right width of the second door is identical to the left and right width of the first door, wherein a rotation direction of the second door is identical to a rotation direction of the first door, wherein the storing device includes: a frame; and a basket (510, 540, 560) installed on the frame, wherein each of the frame and the basket (510, 540, 560) includes at least one second coupling part (425, 445) interacting with at least one of the plurality of first coupling parts (330, 331, 332), wherein a front surface of the second door is positioned to be generally coplanar with at least a portion of a front surface of the first door. a frame; and a basket (510, 540, 560) installed on the frame, wherein each of the frame and the basket (510, 540, 560) includes at least one second coupling part (425, 445) interacting with at least one of the plurality of first coupling parts (330, 331, 332), wherein a front surface of the second door is positioned to be generally coplanar with at least a portion of a front surface of the first door.