We have many small diameter pipes that are cooling pipes for atomic power stations, boiler pipes, and gas or water pipe lines. They must be periodically inspected in order to protect the accident previously. These pipes are different at the place where pipes change from the main to the branch. The inspection robot must move different diameter and generating large traction force for the long distance. We have proposed a snake type in-pipe mobile robot. The fabricated robot is constructed by a moving mechanism and the two brake mechanisms. The robot was confirmed to move in different diameter pipes whose diameters are between 50 mm and 90 mm, generating the traction force of 10 N at 50 mm diameter pipe.