Most of cleaning robots have a disk like body with a diameter of about 300mm and a height of 100mm. However, there are gaps in which robots cannot go ahead in real environments due to the robot's size. In addition, it is impossible to clean up a floor in a neighborhood of obstacles and corners that are easily covered with dust garbage. The objective of this study is to develop a small cleaning robot so as to realize cleaning at gaps in which a conventional robot cannot come in, neighborhoods of obstacles, and corners. The present paper describes a realization method for running along obstacles and gives some experimental results to evaluate the running performance.