A refrigerator includes a cabinet having a storage chamber, a main door pivotably mounted to the cabinet while including an opening provided at;an inside of the main door, and a stepped portion provided around the, opening, a sub-storage chamber mounted at the inside of the main door, a sub-door mounted to the main door, to allow a user to have access to the sub-storage chamber, the sub-door having opposite side surfaces with front portions protruding forwards of a front surface of the main door while having a greater width than the opening and stepped portion between the front portions of the side surfaces, to cover the stepped portion by the side surfaces, and a hinge pivotably mounted to the main door and coupled to the sub-door while being bent at an intermediate portion thereof, to pivotably support the sub-door with respect to the main door.