In this paper, a robot was developed for in-pipe cleaning and inspecting a large number of circular in-pipes of sea plants, ships, and buildings. A pressure generation mechanism was devised to inspect circular in-pipes with different diameters and to move up and down slant or perpendicular slopes in-pipes. For inspection of the dark inner side of the pipe, a light system using LED which dissipats small electricity was developed. Also, a design method was analyzed to decide the capacity of driving motor for the robot when the mass and maximum velocity of the robot are identified. The robot developed based on the design specification, was tested to verify the performance of the pressure generation mechanism. In addition, a control system was developed for the test.