PURPOSE: To reduce a sectional area in a direction vertical to the trans-axle shaft of an electric automobile by providing one of drive shafts coaxially with an output shaft in such a manner to extend through the output shaft.

CONSTITUTION: The output shaft 2 of an electric motor 3 is formed in a hollow state and a right drive shaft 5R is arranged coaxially with the output shaft 2 in such a manner to extend through the output shaft 2, whereby the sectional area of an electric motor 3 forms the sectional area of a trans-axle 1. Thereby, the size and the weight of a trans-axle case 7 are reduced. Further, since the output shaft 2 is drive shafts 5R and 5L which are arranged on the same axis as each other, the center of gravity of the trans-axle 1 is positioned on the drive shafts 5R and 5L. Thereby, when the trans-axle 1 is arranged on a front wheel, the height of a hood can be reduced and the trans-axle can be mounted on an automobile using a present engine serving as a power without sharply varying a car body structure.