Refrigerator

A refrigerator comprising:

• a cabinet defining a storage compartment;
• a main door having a front surface and a rear surface, the main door being rotatably connected to the cabinet and configured to open and close the storage compartment;
• an auxiliary storage compartment provided to the rear surface of the main door, an access opening being provided in the main door to allow access to the auxiliary storage compartment from the front surface of the main door;
• a sub-door having a front surface and a rear surface, the sub-door being rotatably connected to the main door and configured to open and close the access opening such that, based on the sub-door being oriented in a closed position, the rear surface of the sub-door contacts the front surface of the main door to close the access opening;
• a button exposed at the front surface of the sub-door and configured to receive input provided by a user;
• a hook member having a pivot shaft mounted to a rear end the hook member, the hook member protruding backward from the rear surface of the sub-door and being configured to rotate within the sub-door about the pivot shaft in response to receipt of user input at the button;
• a locking protrusion provided in a groove located on the front surface of the main door and configured to be selectively coupled to the hook member;
• and
• a link member coupled to the hook member and configured to rotate together with the hook member in response to receipt of user input at the button.