A steering handle 11 is connected to a front-left wheel FW1 via first and second steering shafts 12 and 13, a pinion gear 14 and a rack bar 31. The pinion gear 14 is connected to a front-right wheel FW2 via third to fifth steering shafts 15, 16 and 23, a pinion gear 24 and a rack bar 34. A first differential gear mechanism 40 is interposed between the first and second steering shafts 12 and 13, whereby the rotation of an electric motor 49 realizes the difference in the rotation between the input shaft and the output shaft of the first differential gear mechanism 40. A second differential gear mechanism 50 is interposed between the third and fourth steering shafts 15 and 16, whereby the rotation of an electric motor 59 realizes the difference in the rotation between the input shaft and the output shaft of the second differential gear mechanism 50. Therefore, the pair of left and right steering wheels FW1, FW2 are steered independently, thereby enhancing maneuverability of a vehicle.