This paper proposes an in-pipe robot adaptable to pipe diameter change. The robot can adapt to 400 to 700 mm diameter piping. A pantograph mechanism provides the adaptability and the robot drives using tracks. One track module consists of front and rear tracks connected by an active joint with structural compliance. Its passive foldable characteristics provide information of the frontal space and help keeping contact with the surface on which it travels. This paper also suggests two control algorithms. One is a method to keeping proper normal force without pressure sensors. The other is a posture control to move in curved pipe by pantograph angle detection. These algorithms are verified by experiment.