A frictional propulsion device, comprising: a frame; a main wheel including an annular core member having a laterally extending central axial center line and a plurality of driven rollers each rotatably supported on the annular core member about a tangential line of the annular core member; a support shaft supported by the frame and extending laterally across a hollow interior of the main wheel; a pair of drive disks rotatably supported by the support shaft on either side of the main wheel, the drive disks being individually rotatable around a central axial line common to the support shaft; a plurality of drive rollers arranged along a peripheral part of each drive disk and each rotatably supported by the drive disk 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, at least part of the drive rollers engaging the driven rollers of the main wheel; a drive unit mounted on the frame; and a transmission mechanism (80, 86, 88) for transmitting power from the drive unit to the drive disks individually; wherein a diameter of a drive side contact circle defined by points on the drive disk at which the drive rollers contact the driven rollers is smaller than a diameter of a driven side contact circle defined by the points on the main wheel at which the driven rollers contact the drive rollers, 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; and wherein the drive unit is positioned in a crescent shaped space defined between an outer peripheral part of the drive disks and an inner peripheral part of the main wheel as seen from a side. a frame; a main wheel including an annular core member having a laterally extending central axial center line and a plurality of driven rollers each rotatably supported on the annular core member about a tangential line of the annular core member; a support shaft supported by the frame and extending laterally across a hollow interior of the main wheel; a pair of drive disks rotatably supported by the support shaft on either side of the main wheel, the drive disks being individually rotatable around a central axial line common to the support shaft; a plurality of drive rollers arranged along a peripheral part of each drive disk and each rotatably supported by the drive disk 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, at least part of the drive rollers engaging the driven rollers of the main wheel; a drive unit mounted on the frame; and a transmission mechanism (80, 86, 88) for transmitting power from the drive unit to the drive disks individually; wherein a diameter of a drive side contact circle defined by points on the drive disk at which the drive rollers contact the driven rollers is smaller than a diameter of a driven side contact circle defined by the points on the main wheel at which the driven rollers contact the drive rollers, 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; and wherein the drive unit is positioned in a crescent shaped space defined between an outer peripheral part of the drive disks and an inner peripheral part of the main wheel as seen from a side.