The movements of snake robots are often studied in specific environments, such as two-dimensional planes, the insides or outsides of pipes, or through water. However, snake robots are also expected to be deployed in more complex environments such as disaster sites, which require more adaptability than simple environments. To realize adaptability, a snake robot needs reflective behavior in its control system for obstacle encounters. Although obstacle-adaptation methods have been proposed, most of them are limited to two-dimensional movement. This research proposes a reflexive behavior that adapts to obstacles by changing the curvature of the snake robot in a three-dimensional environment. To apply and verity the proposed method, we developed a snake robot with full-circumference pressure sensors, and moved it along a pipe by a helicoidal rolling motion. The experimental result showed that the snake robot can adapt to an obstacle by adopting reflexive behavior.