The jigsaw puzzle has been popular from past to present, and there are many jigsaw puzzle images on the Internet. This paper proposes a novel method to hide secret data in jigsaw puzzle images. First, a digital image is taken as input and divided into blocks. Then, a semicircle is drawn and attached to the right and bottom sides of each block. The secret data are embedded through the attached positions and orientations of the semicircles according to a stegokey. The resulting image looks like those jigsaw puzzle images appearing on many jigsaw puzzle Web sites. Experiments show that the proposed method is undetectable under the passive warden and robust to format conversion, lossy compression, and lossy recompression.