Within a moving robot of narrow footprint, having quick traveling performance on a plane-surface, as well as, anti-tumbling function, and further being suitable for operations under coexistence with a human being, being able to travel coping with traveling situations on a level difference, etc.: in front and rear of main driving wheels 2 and 3, each being controlled through the inverted pendulum control, are disposed supporting legs 4 and 5, tips of which can be lifted up and down, wherein the tips of the supporting legs 4 and 5 are positioned to keep a predetermined distance between a traveling surface, when running on the inverted two-wheels travel, and the supporting legs 4 and 5 are fixed or either one in the fall-down direction is thrust out into the fall-down direction, so as to protect it from falling down. Further, upon the basis of detection information of floor-surface distance sensors 4e and 5e and side-surface distance sensor 4f, 4g, 5f and 5g, which are provided at the tips of the supporting legs 4 and 5, the robot senses an existence of a level difference and/or an inclined surface, so as to let the supporting legs to escape from the level difference and/or the inclined surface, and holds the position of gravity center thereof, stably, through other one of the supporting legs, being landed on the ground, and the main driving wheels 2 and 3; thereby enabling to travel over the level difference and the inclines surface.