In a frictional propulsion device comprising a frame, 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 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, each drive disk includes a hub rotatably supported by the support shaft, a disk member attached to a peripheral part of the hub, and holder beams arranged circumferentially between the hub and the disk member such that each holder beam is attached to the hub at a first end thereof and to the disk member at a second end thereof, each drive roller being rotatably supported by a corresponding adjoining pair of holder beams.