Upper Structure of Rear Pillar of Vehicle with Reinforced Stiffness

An embodiment upper structure of a rear pillar of a vehicle includes a roof side member disposed on a side surface of a roof in a length direction of the vehicle, a roof center member disposed at a rear end of the roof in a width direction of the vehicle and connected to a side surface of a rear end of the roof side member, and a seat belt mounting member connected to an end portion of the roof side member.