To provide a rear suspension system of a vehicle equipped with a rear suspension mounting bracket for facilitating the assembly of a rear suspension and reducing the inside noise of a vehicle, by modulatively mounting a suspension device.

This rear suspension system of a vehicle is composed of: a rear axle wherein the respective ends of which are connected to two knuckles to be mounted by a rear wheel in wheel housings their centers are fixed to a vehicle body, and the housings are formed on the right and left sides of the vehicle body; upper and lower arms wherein one end is connected to the upper and lower parts of the knuckles respectively; suspension mounting brackets fixed to the side walls of the housings and connected to one end of the upper arm; and a shock absorber that its upper side part is inserted into the inside of the brackets for absorbing a shock transmitted from the wheel, and the lower side part is connected to the lower arm.