To enable steering of a driving wheel 9, and to give a travelling force auxiliary function relative to the driving wheel 9.

A bracket 2 is supported rotatably around a vertical turning axis 1a in the lower side of a load-carrying platform 1, and a tilting member 6 is supported in the bracket 2 rotatably around a horizontal tilting axis 7a. The driving wheel 9 is supported in the tilting member 6 rotatably around a horizontal driving axis 8a in one region S1 out of both side regions S1, S2 in a horizontal direction with a vertical surface P passing the horizontal tilting axis 7a of the tilting member 6 as a boundary, and an electric motor 10 rotating the driving wheel 9 is attached in alignment with the tilting member 6 in the horizontal driving axis 8a direction of the driving wheel 9. One end side of a power-storage means 11 is supported in the tilting member 6 by an upper side supporting part in the other region S2, and the other end side of the power-storage means 11 is supported in the bracket 2 by a lower side supporting part. Power is stored in the power-storage means 11 via the upper side supporting part when the tilting member 6 is rotated around the horizontal tilting axis 7a.