PURPOSE: To arrange a running motor and a reduction gear so as to suit to the shape of a front floor tunnel for saving a space required for installation by separating a front wheel differential gear and the reduction gear from each other, and arrangedly providing the reduction gear being smaller in diameter than the running motor at its rear part.

CONSTITUTION: A front floor tunnel 13 opening toward the rear part of the front chamber of the car body 11 of an electric vehicle formed by altering a gasoline car is formed in a tapered shape enlarging forward, and a running motor 14 is longitudinally provided in the floor tunnel 13, and a reduction gear 31 linked to the rear part of the running motor 14 is also provided in the tunnel 13. Since the reduction gear 31 is formed smaller in diameter than the running motor 14, the floor tunnel 13 can receive the running motor 14 and the reduction gear 31 to realize a space saving lay-out suited to the shape of the floor tunnel 13. A front wheel differential gear 15 is firmly provided in the front part of the running motor 14, and a front axle 17 is extendingly provided on the right and left of the front wheel differential gear 15.