In a frictional propulsion device comprising a main wheel including driven rollers rotatably supported by an annular core member about a tangential direction and a pair of drive disks each carrying a plurality of drive rollers rotatable about a rotational center line at an angle with respect to both a tangential line of the drive disk and the rotational center line of the drive disk such that the drive rollers at least partly engage the driven rollers, a diameter of a drive side contact circle is smaller than a diameter of a driven side contact circle, and the drive disks are vertically offset relative to the main wheel so that only those drive rollers adjoining the main wheel are in contact with the driven rollers.