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 sub-door coupled to the main door via an upper hinge and a lower hinge , and having a front surface, a rear surface and edge surfaces, and being configured to rotate in a direction identical to the main door ; characterized by a handle groove configured to allow a user to pull the sub-door , the handle groove being inwards recessed from one of the edge surfaces, and forming a shape similar to a rectangular plate; a groove portion disposed beside the handle groove in a line parallel with the front surface of the sub-door and communicated with the handle groove ; an axial groove formed within the handle groove ; a lever member having a pivot axial protrusion , 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 hook member including an upper extension portion extending upwards from a pivot axis portion of the hook member to be pivoted when a user pivots the lever member , and a rear extension portion extending rearwards from the pivot axis portion and a hook provided at an end of the rear extension portion , a bracket having a groove coupled to the axial protrusion of the hook member and mounted on the groove portion; an engagement groove provided at the front surface of the main door and being configured to be hung up by the hook ; and an elastic member being 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 sub-door coupled to the main door via an upper hinge and a lower hinge , and having a front surface, a rear surface and edge surfaces, and being configured to rotate in a direction identical to the main door ; characterized by a handle groove configured to allow a user to pull the sub-door , the handle groove being inwards recessed from one of the edge surfaces, and forming a shape similar to a rectangular plate; a groove portion disposed beside the handle groove in a line parallel with the front surface of the sub-door and communicated with the handle groove ; an axial groove formed within the handle groove ; a lever member having a pivot axial protrusion , 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 hook member including an upper extension portion extending upwards from a pivot axis portion of the hook member to be pivoted when a user pivots the lever member , and a rear extension portion extending rearwards from the pivot axis portion and a hook provided at an end of the rear extension portion , a bracket having a groove coupled to the axial protrusion of the hook member and mounted on the groove portion; an engagement groove provided at the front surface of the main door and being configured to be hung up by the hook ; and an elastic member being disposed within the groove portion and configured to provide an elastic force to the hook member to hang up on the engagement groove . <EOS>