A structure of a door a refrigerator capable of reducing the manufacturing cost while providing a simplified manufacturing process and a simplified assembly. The door includes a front surface panel configured to form a front surface of the door and including tempered glass, a rear surface panel configured to form a rear surface of the door such that a foam space is provided between the rear surface panel and the front surface panel, a first frame and a second frame configured to form each side surface of the door and to which the front surface panel and the rear surface panel are supportedly attached, an upper cap and a lower cap configured to form an upper surface and a lower surface of the door, respectively, and thermal insulating material which is provided in the foam space to couple the front surface panel, the rear surface panel, the first frame, the second frame, the upper cap, and the lower cap to one another, wherein each of the first frame and the second frame is formed by sequentially introducing a steel plate coil having a predetermined thickness and width into a predetermined number of roll forming members.