A refrigerator comprising: a cabinet having a storage chamber; a main door having a front opening and configured to open or close the storage chamber; a plurality of racks mounted on the main door; a sub-door having an outdoor, a door liner, a cap decoration (230, 250) assembled to the outdoor, and foam filled within a space defined by the outdoor, the door liner, and the cap decoration (230, 250), and configured to open or close the opening of the main door; a handle groove configured to allow a user to pull the sub-door inwards recessed from a portion of the cap decoration, and forming a shape similar to a rectangular plate; characterized by a groove portion disposed beside the handle groove in a line parallel with the front surface of the sub-door and communicating with the handle groove; an axial groove formed within the handle groove; a lever member having pivot axial protrusions, which pivots on the axial groove, and configured to back and forth rotate within the handle groove and forming a shape similar to a rectangular plate; a lever integrally formed in a surface of the lever member; a hook member having a first extension portion to contact with the lever and being transferred force from the lever member and a hook bent from the first extension portion and protruding rearwards from the rear surface of the sub-door, the hook member being vertically rotated at an axial protrusion; a bracket having a groove coupled to the axial protrusion of the hook member and mounted on the groove portion: an engagement groove provided on a front surface of the main door and configured to be hung up by the hook; and an elastic member disposed within the groove portion and configured to provide an elastic force to the hook member to hang up on the engagement groove. a cabinet having a storage chamber; a main door having a front opening and configured to open or close the storage chamber; a plurality of racks mounted on the main door; a sub-door having an outdoor, a door liner, a cap decoration (230, 250) assembled to the outdoor, and foam filled within a space defined by the outdoor, the door liner, and the cap decoration (230, 250), and configured to open or close the opening of the main door; a handle groove configured to allow a user to pull the sub-door inwards recessed from a portion of the cap decoration, and forming a shape similar to a rectangular plate; characterized by a groove portion disposed beside the handle groove in a line parallel with the front surface of the sub-door and communicating with the handle groove; an axial groove formed within the handle groove; a lever member having pivot axial protrusions, which pivots on the axial groove, and configured to back and forth rotate within the handle groove and forming a shape similar to a rectangular plate; a lever integrally formed in a surface of the lever member; a hook member having a first extension portion to contact with the lever and being transferred force from the lever member and a hook bent from the first extension portion and protruding rearwards from the rear surface of the sub-door, the hook member being vertically rotated at an axial protrusion; a bracket having a groove coupled to the axial protrusion of the hook member and mounted on the groove portion: an engagement groove provided on a front surface of the main door and configured to be hung up by the hook; and an elastic member disposed within the groove portion and configured to provide an elastic force to the hook member to hang up on the engagement groove. an engagement groove provided on a front surface of the main door and configured to be hung up by the hook; and an elastic member disposed within the groove portion and configured to provide an elastic force to the hook member to hang up on the engagement groove.