PURPOSE: To eliminate the relative movement of the input shaft of a power steering unit to a pivot turned by a steering handle, which movement is caused by swing of a front axle housing, for smooth steering by connecting the input shaft to the pivot through a flexible shaft.

CONSTITUTION: A bracket 17 is mounted on a front axle housing 14, and a power steering unit 19 is mounted on the bracket 17. Further, a drive shaft 22 rotatably supported by a bearing 21 on a car body 16 is connected to an input shaft 23 of the power steering unit 19 through a flexible shaft 24 such as expansible universal joint shaft or flexible wire, and a handle shaft 26 on which a steering handle 25 is mounted is connected to the drive shaft 22 through universal joint shafts 27a, 27b. And when the steering handle 25 is operatively turned, the output shaft 28 is turned to pivot a pivot arm 29, and a knuckle arm 31 pivotably steers front wheels 8.