A flexible incremental roll forming process has been developed by adopting the advantages of the incremental forming process and the roll forming process: i.e., inherent flexibility of the incremental forming process and continuous bending deformation of the roll forming process. It has an adjustable roll set as a forming tool composed of one upper center roll and two pairs of lower support rolls, which plays a key role. Through the experiments, it is shown that the improved forming method of the proposed process is effective in the manufacture of various doubly curved sheet metals, and the proposed relationship of the experimental parameters and the radius of curvature of the formed sheet boundary is useful to control the final shape.