PROBLEM TO BE SOLVED: To provide a gauge variable truck for rolling stock, capable of controlling any unsprung weight increase as securing its steerability.
SOLUTION: A truck 1 is equipped with a truck frame 11, an axle spring 17, an axle box 19, an axle 31, a wheel 41, a motor 61 and a reduction gear 67 or the like. The axle 31 is made into a rotary type so as to be rotatively drivable by means of a Cardan driving system. On this axle 31, the wheel 41, an outer cylinder 35 and an outer cylinder bearing 25 are all sliding left and right, performing a gauge alteration. During this gauge alteration, the outer cylinder 35 and the wheel 41 are going down. In the axle box 19, two clamping grooves 21f and 21d locking the outer cylinder bearing 25 at two spots in this axle box in both directions are installed there.