A method of designing the form of a cable clamp and cables using a three-dimensional CAD system for easily designing the form of the cables passing through the cable clamp is disclosed. According to the method, the cable clamp is checked by comparing the area necessary for clamping the cables with the inner-diameter area of the cable clamp; the control points related to the cable clamp are designated; and the data of the designated control points are added to the data of control points assigned to each cable in advance. Therefore, the form of the clamped portion of each cable can be simultaneously determined together with the forms of the other portions of the cable, so that the designer can execute the verification of the cable clamp and the design of the cable forms in a short time.