A refrigerator comprising: a cabinet configured to define a storage space; a main door configured to open and close the storage space and having an opening; a sub-door configured to open and close the opening by rotating in a same direction as the main door and including an outer case defining a front surface and a door liner defining a rear surface, wherein the sub-door includes: an operation unit mounted at a lower side of the sub-door to be operated by a user's operation; a latch unit spaced apart upwardly from the operation unit and mounted to protrude from a rear surface of the sub-door toward the main door; and a connection unit configured to connect between the operation unit and the latch unit such that the latch unit is operated according to operation of the operation unit; wherein the main door includes a latch accommodating portion formed at a position corresponding to a position of the latch unit such that the latch unit is selectively held and constrained; wherein the connection unit includes: a connection member configured to move in a first direction to operate the latch unit when the operation unit is operated; and a connection member case (422, 423) forming a space for accommodating the connection member, wherein, the connection member case (422, 423) includes at least one protrusion (426, 427) protruding toward the connection member so as to prevent movement in a second direction crossing the first direction when the connection member moves in the first direction, characterised in that: the connection member case (422, 423) includes a first connection member case provided at a front of the connection member case, and a second connection member case provided at a rear of the connection member case and mounted on the door liner; and the at least one protrusion (426, 427) includes a first protrusion protruding from a rear surface of the first connection member case toward a rear, and a second protrusion protruding from a front side of the second connection member case toward a front. a cabinet configured to define a storage space; a main door configured to open and close the storage space and having an opening; a sub-door configured to open and close the opening by rotating in a same direction as the main door and including an outer case defining a front surface and a door liner defining a rear surface, wherein the sub-door includes: an operation unit mounted at a lower side of the sub-door to be operated by a user's operation; a latch unit spaced apart upwardly from the operation unit and mounted to protrude from a rear surface of the sub-door toward the main door; and a connection unit configured to connect between the operation unit and the latch unit such that the latch unit is operated according to operation of the operation unit; an operation unit mounted at a lower side of the sub-door to be operated by a user's operation; a latch unit spaced apart upwardly from the operation unit and mounted to protrude from a rear surface of the sub-door toward the main door; and a connection unit configured to connect between the operation unit and the latch unit such that the latch unit is operated according to operation of the operation unit; wherein the main door includes a latch accommodating portion formed at a position corresponding to a position of the latch unit such that the latch unit is selectively held and constrained; wherein the connection unit includes: a connection member configured to move in a first direction to operate the latch unit when the operation unit is operated; and a connection member case (422, 423) forming a space for accommodating the connection member, a connection member configured to move in a first direction to operate the latch unit when the operation unit is operated; and a connection member case (422, 423) forming a space for accommodating the connection member, wherein, the connection member case (422, 423) includes at least one protrusion (426, 427) protruding toward the connection member so as to prevent movement in a second direction crossing the first direction when the connection member moves in the first direction, characterised in that: the connection member case (422, 423) includes a first connection member case provided at a front of the connection member case, and a second connection member case provided at a rear of the connection member case and mounted on the door liner; and the at least one protrusion (426, 427) includes a first protrusion protruding from a rear surface of the first connection member case toward a rear, and a second protrusion protruding from a front side of the second connection member case toward a front. the connection member case (422, 423) includes a first connection member case provided at a front of the connection member case, and a second connection member case provided at a rear of the connection member case and mounted on the door liner; and the at least one protrusion (426, 427) includes a first protrusion protruding from a rear surface of the first connection member case toward a rear, and a second protrusion protruding from a front side of the second connection member case toward a front.