In this paper, we propose a method for priority-based medical image forwarding over DTN (delay-tolerant networks), in which an important part (injured part) in a patient’s picture is detected and assigned a high priority, and forwarded faster in DTN. In our method, we suppose a disaster scenario where medical doctors in a disaster area take a picture of the injury and send it to the main hospital for getting information of appropriate treatment. DTN is a promising technology used for transmitting images from the disaster area to the hospital in an environment where no high speed cellular networks are available. However, transmitting a high-resolution medical image over DTN is a challenging task. Our proposed method aims to solve this problem by introducing image segmentation and priority forwarding techniques into a conventional DTN. Focusing on eye injury in a volcano disaster, we developed an algorithm to divide each patient’s picture into pieces and assign a priority to the pieces containing the injury part in the picture with color marking. We also employ a scheduling methods for priority based message forwarding, in which the intermediate node in DTN forward high priority pieces before other pieces. As a result, an important part of a picture, which is mandatory for diagnosis, will arrive at the main hospital faster than other parts. Through a computer simulation, we confirmed that the proposed method could deliver diagnosable images faster than a conventional method.