A refrigerator includes a cabinet, a main door having an opening, a sub-door rotatably provided in front of the main door to open and close the opening and filled with a heat insulating material, a locking member protruding from the sub-door to the main door and operated to lock the main door, an operation member provided below the locking member and protruding downward from a lower portion of the sub-door to be directly operated by a user, a connection member connecting the locking member and the operation member such that the locking member operates when the operation member operates, and a connection member case provided inside the sub-door and defining a space in which the connection member is operatively accommodated. The connection member case is formed with a reinforcement part extending in an upper-and-lower direction along the connection member case to prevent deformation of the connection member.