Recently, many pipeline inspection robot systems have been developed. We develop a reconfigurable robot that can be used for 80~100 mm pipeline. First of all, we derive the kinematics of this mechanism and determine the actuator size by static analysis. The mechanism consists of three pairs of caterpillar, each of which is operated by a micro DC motor. The robot is designed foldable when each chain contacts the wall of pipelines. Thus, the robot can be operated in various sizes of pipeline. Controlling the speed of caterpillar independently provides a steering capability. So it can go through elbow and T-branch. The robot system has been developed and the validity of this mechanism was proved by experimentation.