To optimize a gap between a spring bracket and a leaf spring by making the spring bracket mounting position of a trunnion type rear axle housing device adjustable in the lateral direction of a vehicle and improve operating stability when making a turn by minimizing motion of an unsprung member with respect to the leaf spring in the lateral direction of the vehicle.

A mounting part 21a is formed on a rear axle housing 21 and a slotted hole 22d longish in the lateral direction of a vehicle is formed on a spring bracket 22, while the spring bracket 22 is sandwiched between a wear sheet 25 and the rear axle housing 21 mounting part 21a and temporarily fitted to each other by inserting a bolt 26 through the slotted hole 22d and the spring bracket 22 is adjusted within the range of the slotted hole 22d at the final assemblying process by moving the spring bracket 22 in the lateral direction of the vehicle so that a gap S between a leaf spring 30 and the spring bracket 22 may become an optimum gap S.